Development of Biochemical Concepts from Ancient to Modern Times [2nd printing 1975. Reprint 2014 ed.] 9780674864252, 9780674864122

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Development of Biochemical Concepts from Ancient to Modern Times

Harvard Monographs in the History of Science

Harvard Monographs in the History of Science Chinese Alchemy: Preliminary Studies by Nathan Sivin Leonhard Rauwolf: Sixteenth-Century Physician, Botanist, and Traveler by Karl H. Dannenfeldt Reflexes and Motor Integration: Sherrington's Concept of Integrative Action by Judith P. Swazey Atoms and Powers: An Essay on Newtonian Matter-Theory and the Development of Chemistry by Arnold Thackray The Astrological History of Mäshä' alläh by Ε. S. Kennedy and David Pingree Treatise of Man: Rene Descartes French Text with Translation and Commentary by Thomas Steele Hall

Editorial Committee I. Bernard Cohen (chairman) Donald H. Fleming Gerald Holton Ernst Mayr Everett I. Mendelsohn John E. Murdoch

Development of Biochemical Concepts from Ancient to Modern Times

Henry M. Leicester

Harvard University Press Cambridge, Massachusetts, and London, England

© Copyright 1974 by the President and Fellows of Harvard College All rights reserved Second printing 1975 Library of Congress Catalog Card Number 73-83965 ISBN 0-674-20018-7 Printed in the United States of America

Preface

O n e of the m a j o r problems in p r e p a r i n g a history of biochemistry is t h e question of w h e r e to d r a w the line between historical a n d m o d e r n material. T h e rate of d e v e l o p m e n t of t h e science has been so r a p i d that it sometimes seems that material of ten years ago has already b e c o m e "classical." I n t h e p r e s e n t work the line has been placed m o r e or less arbitrarily in t h e d e c a d e of the 1930s. However, t h e great concept of t h e function of t h e nucleic acids has h a d to b e m e n t i o n e d at t h e e n d , since this has so closely knitted tog e t h e r all of t h e work which has g o n e b e f o r e . A n o t h e r p r o b l e m is how to deal with t h e e n o r m o u s a m o u n t of factual a n d theoretical material which is available. T h i s p r o b l e m has b e e n faced in various ways. Fritz Lieben in his s t a n d a r d work, Geschichte der physiologischen Chemie (Franz Deuticke, Leipzig a n d Vienna, 1935; r e p r i n t e d by G e o r g Olms Verlag, Hildesheim a n d New York, 1970) fitted his topics into t h e general history of chemistry a n d described in considerable detail t h e discovery of individual c o m p o u n d s a n d reactions. Necessarily in such an ap-

proach the emphasis lies on relatively m o d e r n work. I have chosen rather the approach of a history of concepts. Biochemical concepts in the sense in which I have used the term refer to any hypotheses of bodily function which involve specific substances. Concepts of this sort have been present at all periods, in all h u m a n thought a n d speculation. T h e r e f o r e their treatment in this book covers the long period which precedes m o d e r n biochemistry as well as the m o r e recent work. Historians of science are now generally agreed that we should not attempt to read a m o d e r n viewpoint into the ideas of an earlier period. A writer must be considered in the context of his own day. Yet when the broad field is surveyed we can see similar f u n d a m e n tal ideas t h r o u g h o u t history. T h e most basic idea of biochemistry, the concept that life is the result of a balance of interacting forces, was as familiar to Aristotle and Galen as it is to the m o d e r n scientist tracing the paths of metabolism. T h e basic thought remains; the interpretations change as new facts accumulate. Concepts build on previous concepts. Tracing the development of these concepts f r o m ancient to m o d e r n times is not a reading of o u r ideas into the ancients. It is a process of observing the response of the h u m a n mind to the conditions a r o u n d it. This is why the history of biochemistry, like the history of any science, possesses a continuity which is fascinating to follow. I would like to take this opportunity to thank my colleague, Aldo Ν. Corbascio, who has read most of this manuscript and o f f e r e d many valuable suggestions. T h a n k s are d u e to the University of Pennsylvania Press for permission to use my article "Biochemical Concepts a m o n g the Ancient Greeks" (Chymia 7: 9-35, 1961) as a basis for Chapters 2 and 3. H.M.L.

Contents

1 2 3 4 5 6 7 8 9 10 11 12 13 14

The Earliest Concepts Biochemical Concepts in Classical Greece The Hellenistic Period The Early Middle Ages Chinese and Indian Concepts Arabic Concepts The Medieval Period Paracelsus and the Beginnings of latrochemistry The Transitional Seventeenth Century Physiology Comes of Age Pneumatic Chemistry and Its Biological Significance Animal Chemistry Nineteenth-Century Vitalism Theories of Digestion and Assimilation in Mid-nineteenth Century 15 Enzymes and Cell Constituents 16 Energy Production and Biological Oxidations 17 Intermediary Metabolism 18 Vitamins 19 Hormones 20 Afterword Index of Proper Names Subject Index

1 5 25 37 44 53 63 81 92 111 128 138 149 160 176 189 201 212 223 231 275 281

1 The Earliest Concepts

Biochemistry can be defined most simply as the study of the composition of living organisms and the mechanisms by which the various components interact to produce the changes in metabolism and function that make life as we know it. Thus, biochemistry is concerned with an explanation of the processes of the body in terms of material substances, so that any theory which explains a mechanism in terms of such substances can be called a biochemical concept. Obviously, only in recent times has enough been learned of the chemical nature of the living cell to permit any sort of accurate formulation of such mechanisms. Nevertheless, the phenomena of life are so striking and the natural interest of man in the functioning of his body in health and disease is so great, that ever since he began to reason at all he has evolved theories—sometimes highly speculative, sometimes more reasonably based—to explain the nature of the living world. His speculations at first must have fitted into the magicoreligious framework by which primitive man tried to order the incomprehensible forces which surrounded him. His earliest efforts resulted in endowing all nature with life, so that any event, whether in the physical world or in his own body, was the result

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Development of Biochemical Concepts

of some benign or malevolent being willfully affecting him. Legends grew up to explain the origin of his tribe, and a class of medicine men was set aside to preserve these legends and to control the spirits which affected his life. As society grew more complex and civilizations developed, the priestly class had time to organize the legends, develop the religions, and speculate more logically on the world around it. In all the major civilizations with which we have any considerable acquaintance these speculations were ultimately organized into systems of philosophy which sought to explain all the facts known to the philosophers. T h e civilizations best known for their all-embracing philosophical systems are those of Greece, China, and India. Each of these systems apparently was developed more or less independently, and each is highly characteristic. In their later histories there was some interaction between them, and there is some disagreement as to whether they had some early contacts. At any rate, there is no doubt that certain major ideas are common to all of them, and these ideas formed the basis for many of the more specifically biochemical concepts that will be discussed later. One of the most generally accepted beliefs must have been a primitive animism, but the original idea of endowing all nature with life had to be abandoned in its first form as the distinction between the inorganic and the organic worlds became evident. True, the sun and moon might be considered to be gods, but they were recognized as being fundamentally different from men and animals on earth. Continued observation showed regularities in the behavior of astronomical bodies which could not be found in capricious animal life. A science, astronomy, was born. Yet there were irregularities, even in the heavens. Comets and eclipses disturbed the regularities of heavenly events, just as plagues and wars disturbed human life. Thus animism assumed a new and more sophisticated guise. T h e two sets of disturbances could be correlated and then related in terms of cause and effect. The concept arose that events occurring in the great world of nature, the macrocosm, were reflected in the events of the little world of man, the microcosm. This macrocosm-microcosm theory assumed great importance in biological thinking and retained its influence even down to comparatively recent times.

T h e Earliest Concepts

3

A second general idea underlay much philosophical speculation. When a man looks around himself, he observes on every hand pairs of opposite qualities. Heat and cold, male and female, wet and dry; the world seems to be made up of contraries. How to reconcile the unity and order of this world with the presence of these ubiquitous opposites was one of the chief problems of the philosophers, and much ingenuity was employed in devising methods for reaching a balance between them. Finally, on a more strictly biological level, man from the earliest times realized that certain organs in the body were very important or essential to life, while others were less so. It was inevitable that he would speculate as to which organ was vital to life itself. A cave drawing of a mammoth, dating from the Aurignacian period, shows a spot at the location of the heart, and Sigerist has called this the first anatomical picture. 1 More advanced philosophers later debated the relative importance of the heart, liver, and brain; and devised functions for each of these organs. These philosophical ideas formed the basis both for cosmological speculations and for theories of life in the three major civilizations mentioned above. However, the development of modern biological concepts can be traced almost directly from the philosophy of the Greeks, while the philosophies of China and India, interesting though they are, contributed only peripherally to western science. Therefore the Greek biochemical concepts must be discussed in some detail. Greek philosophy did not arise spontaneously, however. T h e early Greek thinkers were the heirs of the civilizations of Mesopotamia and Egypt, in which biochemical concepts had already arisen, and these were subsequently transmitted to the Greeks. Mesopotamian medicine tended to stress the magical approach to disease, and consequently theories of mechanisms in the body were not greatly emphasized. However, the Mesopotamians employed a highly systematic method in studying the world around them. The Sumerians began and the Babylonians continued the practice of compiling long lists of related subjects. Thus, in the field of pharmacology, where magic was relatively disregarded, they left extensive lists of the drugs they used, 2 and this systematic approach remained basic to any scientific disci-

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Development of Biochemical Concepts

pline. They considered the liver to be the seat of life and used the appearance of the actual livers from sacrificed animals as signs to be interpreted in their divinations. Their application of the macrocosm-microcosm theory led them to the pseudo-science of astrology, which they developed more highly than did any other early culture. The importance which the Greeks placed on this theory was probably due in large measure to the Babylonian emphasis, though the Greeks did not accept its astrological aspects so completely. The Egyptians were a somewhat more practical people than the Babylonians, and their practice of mummification gave them a close acquaintance with many aspects of the human body. They were greatly interested in respiration and blood. They regarded the heart as the center of the vascular system. All "vessels" depended on it. These vessels were vehicles not only of blood but of air, water, mucus, semen, and other secretions. 3 They believed that diseases were caused by superfluities or residues of food taken into the body. They had observed putrefaction in dead bodies, and the practice of mummification was designed to prevent this and to preserve the body. Similarly, the physician attempted to eliminate putrefactive material from the body of the sick man. If he did not, the noxious material from putrefaction in the intestine could enter the blood and eventually form pus. Control of the diet was thus important. 4 These ideas were to be found later in some Greek medical theories, and they are one of the first clear examples of a material cause assumed for a bodily mechanism, that is, a biochemical concept as defined above.

2 Biochemical Concepts in Classical Greece

Greek philosophy arose in the Ionian city of Miletos in the sixth century B.C. This fact is understandable, for Miletos was a great trading center, in contact with the cultures of Mesopotamia to the east by land through Syria and Lydia, and with Egypt to the south by sea through the city of Naucrates at the mouth of the Nile, which was a commercial center largely occupied by Greeks at the time.' Thus the ideas of both Mesopotamia and Egypt could stimulate the lively Greek mind, and Greek philosophy developed rapidly. In classical times the Greek thinker, the philosopher, was both intensely curious and intensely logical. He observed the world around him and carefully noted its important features. He placed these features in their obvious or apparent relationships, he classified them, and he developed theories to explain why they behaved as they did. However, differing from modern scientists, he did not, in most cases, attempt to test his theories once they had been formulated. If the canons of logic were satisfied, so was he. Thus a large number of explanations might be derived from

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Development of Biochemical Concepts

a single set of observations or on the basis of a single theory, though no experimental attempt was made to decide between them. Each thinker accepted the theories that most appealed to him. Naturally, some men were more interested in observing and classifying, while others preferred to devise theories, but in almost every case the thinking of the Greek intellectual involved a mixture of both procedures. Those who objected strongly to the theories of others devised their own theories to account for the facts they observed. Another characteristic of Greek philosophy was its dissatisfaction with anything less than a complete explanation. T h e philosophers wished to answer every question, to construct universal cosmological theories and to use them to explain all the details of nature. Nature was a very broad term to the Greeks. Hence the philosopher constructed his theories in the light of pure reason, in the way most plausible to him, but he almost never turned back to test his theories. Reason and logic ruled. Parmenides could deny the existence of motion on purely logical grounds, and the fact that he himself moved was irrelevant to his speculations. One of the major reasons why Greeks thought along biochemical lines was that they were greatly interested in biological phenomena. They constructed cosmological theories to explain nature and the interrelations of matter, and they applied these theories to the stars and the great world about them. They also observed the human body in detail in the gymnastic games and in their various schools of medicine. They tried to explain the behavior of the body in terms of their cosmological theories, and as time went on, they began to reverse this process and to apply their biological speculations to the great world about them. In other words, they took the old Babylonian idea of the microcosm and the macrocosm as the basis of their thinking. They used the idea not for astrological purposes but rather as a basis for rational speculation, believing that an understanding of both the macrocosm and the microcosm could be obtained by a study of either one. Hence came the wealth of biochemical theories which expressed the concern of the philosophers for the functioning of all nature.

Classical Greece

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Although the Greeks from the earliest times were interested in medicine and physical fitness, the earliest philosophers were not primarily interested in biological questions. They were concerned with the fundamental nature of the cosmos, and in terms of the physical phenomena around them they tried to derive an explanation of the basic material from which the world was formed. Actually, however, many of the philosophers were physicians. Among physicians there were always men who were interested chiefly in the immediate cure of the patient without bothering about the cause of the disease or in making broad generalizations as to body function. 2 Such men have been called leeches, and leechcraft led ultimately to the formation of a guild concerned with medicine as an art. On the other hand, those who preferred philosophical speculation-went on to devise a theory of medicine. Medicine as a craft had little influence on philosophy, but philosophy strongly influenced medical theory. 3 T h e first Greek philosophical school centered at Miletos, and the earliest Ionian philosophers sought to find the one material of which everything was made. Thales (fl. 585 B.C.) believed this material was water; Anaximander (fl. 547 B.C.) that it was an indefinite and infinite ("boundless") substance, the apeiron; and Anaximenes (fl. 546 B.C.) that it was air. Although the chief interest of these men was cosmological, each made biological applications of his theories. Thus, Anaximander believed that innumerable worlds were constantly arising out of the apeiron and disappearing into it again. An application of this idea led him to a sort of evolutionary theory that living creatures arose out of moisture and man arose from other species, probably from fish.4 T h e concepts which acquired the greatest importance in later Greek biological speculations were those of Anaximenes and Heraklitos (fl. 504-500 B.C.). The first laid emphasis on the importance of air (later developed into the idea of pneuma), and the second on the importance of fire (later, innate heat). By giving priority to air as the primal substance, Anaximenes called attention to this material, so vital for life and so obviously connected with respiration. It should be noted that for him air was a term which also included mists and vapors. 5 This idea had to be much clarified before it could be used by later philosophers in its appli-

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Development of Biochemical Concepts

cation to life. Anaximenes was also responsible for the concept that air followed a "downward path" of condensation to water and earth, and an "upward path" to fire. Thus these substances were thought to be interchangeable, an idea which had later important consequences. Heraklitos made this latter aspect of the theory more precise and more applicable to biological problems. He found the primal substance to be fire, but not a stable fire. The theory of Heraklitos was essentially dynamic. Fire burns continually, but it is always different in its sources and products. Rivers flow, but the water is different. He said: "You cannot step twice into the same rivers, for fresh waters are ever flowing in upon you." 6 Everything is constantly following the downward or upward path of Anaximenes. Change is essential and everywhere. In his attempts to explain the macrocosm, Heraklitos turned to the microcosm, man, who, in his opinion, was composed of fire, water, and earth. 7 Although these substances constantly changed into one anther in accordance with his dynamic theory, the body as a whole did not appear to change. Nevertheless, minor oscillations in the interconversions of the basic substances accounted for such phenomena as sleep and wakefulness. Fire was assumed to be the source of consciousness; when it decreased in overall amount, consciousness was lost and sleep resulted. 8 T h e "soul" was an even balance of fire and water and was thus material. This term "soul" was used by the pre-Socratic philosophers to designate the various manifestations of life. It was a material substance which guided the functioning of the body and was thus imposed on the body. Life was inherent in a living system as much as were air or fire9 and it acted on the body in a mechanical 10 sense. Therefore later philosophers could develop concepts of the existence of different sorts of souls to control different bodily functions. With Empedocles (fl. 440 B.C.) biological theories became much more precise. Empedocles was a physician who founded the Sicilian school of medicine, a school which survived at least until the time of Aristotle. 11 He based his medical teachings on his general cosmological theory. Instead of one primal substance, he assumed that all matter was composed of four "roots," as he called them: fire, air, water, and earth. These were actual substances.

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H e p r o v e d this point in the case of air by his d e m o n s t r a t i o n with the klepsydra, or water clock. W h e n the large o p e n e n d of a conical vessel was d i p p e d into water while the f i n g e r was held over a small o p e n i n g at the opposite e n d , t h e r e was n o entry of water until the f i n g e r was r e m o v e d , a n d t h e n air r u s h e d o u t of the small o p e n i n g as water e n t e r e d t h e large. 1 2 T h i s was o n e of the few physical d e m o n s t r a t i o n s r e c o r d e d f r o m the classical Greek period, a n d its biological significance in proving the corporeal n a t u r e of air was as great f o r later physicians as was its cosmological significance f o r the philosophers. T h e theory of roots was actually the first atomic theory, f o r the f o u r roots were t r u e elements in o u r sense of the word, chemically u n c h a n g e a b l e a n d ultimate. 1 3 At the same time, they were the physical expression of two pairs of opposites which earlier thinkers h a d considered to be very i m p o r t a n t , opposites such as day a n d night, male a n d female, a n d m a n y others of which the world was t h o u g h t to be composed. T h e pairs h e r e r e p r e s e n t e d the physical states of hot a n d cold, moist a n d dry. In addition to his f o u r roots, Empedocles f o u n d it necessary to assume two m o r e to explain the combination a n d splitting of his elements in the changes actually seen in n a t u r e . As a physician, h e t h o u g h t in t e r m s of h u m a n emotions: love b r o u g h t t h e elements together; strife d r o v e t h e m apart. However, love a n d strife were as material as the o t h e r f o u r elements. A n o t h e r i m p o r t a n t part of his theory was that pores existed between atoms t h r o u g h which o t h e r elements could sift and p e n e t r a t e . T h i s concept of pores was e x t e n d e d in various ways in later biological t h o u g h t . Empedocles had a v a g u e · theory of evolution which implied what might b e called the survival of t h e fittest, a n d a theory of the d e v e l o p m e n t of embryos, 1 4 b u t it was in his theory of the comp o n e n t s of organic beings that his chief biochemical concepts were to be f o u n d . T h e m a i n c o m p o n e n t s of the body were fire a n d e a r t h , united by love. W h e n fire p r e d o m i n a t e d , as in birds, the animals t e n d e d to fly u p w a r d . Death was the separation of fire a n d e a r t h by strife, a f t e r which the elements could r e c o m b i n e into new bodies. Obviously this was not a vitalistic doctrine. Empedocles was able to o f f e r a t h e o r y of nutrition. H e believed that like attracts like a n d that each portion of the body attracted to itself certain materials f o r its f u r t h e r construction. T h e s e

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Development of Biochemical Concepts

occupied the positions they did because only they were of the right size and shape to fit into the pores of the similar portion of the body. 15 Everything gave off effluences in the form of particles of distinctive size and shape, and when such effluences reached the sense organs, they produced the characteristic effects of sight, smell, and so on. This doctrine was later elaborated by the Epicureans. Respiration occurred by drawing in air, not only through the nostrils but also through the pores of the skin. Blood moved from the heart to the surface of the body and back, thus alternately expelling air and drawing it in. 16 The heart was the organ of consciousness. 17 A somewhat similar theory of the composition of the body was contained in the cosmological theories of Anaxagoras (c.500-c.428 B.C.), who, like Empedocles, believed in individual structural particles. However, he did not confine himself to four elements but assumed an infinite number of particles ("seeds"), each of which contained portions of everything material. Those which contained a preponderance of one substance tended (under the influence of mind, which controlled them) to combine into that substance. Thus the seeds which contained the most flesh combined to make up flesh, those with most bone, bone, and so on. 18 Another idea, implicit in the thinking of some of the philosophers already discussed, was that of balance in the components of the body. This concept was very appealing to the Greek mind, which always rejoiced in order. It was particularly emphasized by the mystic school of the Pythagoreans, who laid great stress on the properties of numbers. The principles of harmony were traditionally discovered by Pythagoras and his followers, and this led to the idea of the harmonic mean. It can be seen that by the end of the fifth century B.C. the Greek philosophers had evolved a series of basic ideas which could be used to explain a great number of facts. These included the idea of a series of elemental substances whose properties were based on the physical qualities of hot, cold, moist, and dry, with particular emphasis on fire and air; the theory that the balance of these properties could account for much of what was observed; and the biological approach to problems which was founded on the theory of the macrocosm and the microcosm.

Classical Greece

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T h e applications of these theories could be, and were, many and various. Depending on the relative importance ascribed to air or fire, to the degree of balance of the components, to practical observations, or to theoretical speculation, it was possible to find many explanations for a given fact, but the basic approach was essentially the same. It will not be possible in what follows to trace all the varieties of physiological theory, but it is possible to show the main lines of Greek thought leading to the ideas of Galen, which dominated biochemical thinking for nearly 1500 years. The first important name in the more restricted field of biochemical concepts is that of the physician Alkmaion of Kroton, who flourished about 500 B.C. 19 He may have belonged to the Pythagorean sect or have been closely connected with it, though there is some reason to doubt this. 20 He combined the older doctrine of pairs of opposites with the concept of harmony of the Pythagoreans. He held that health was a blending of opposite powers, of which there were a great many in the human body. These included hot, cold, moist, dry, bitter, sweet, and many others. It should be particularly noted that these opposites were many in number and were not substances, but "powers," that is, somewhat indefinite qualities. It was only later that these qualities became corporeal. Alkmaion thought that health existed when there was an equilibrium of all these powers and that disease occurred when any one of them assumed a "monarchy" or dominance over the others. This doctrine of balance was the direct inspiration for the later humoral theory. Empedocles carried on this idea of equilibrium, but he reduced the number of opposites to the four roots: fire, water, earth, and air. He thus gave a material basis to the powers of Alkmaion, for his roots were true substances. He also introduced the number four into physiological thought. T h e first really extensive applications of these ideas to actual biochemical mechanisms are found in a number of works in the Hippocratic Corpus. This is a varied collection of some seventy works, dating chiefly from the years 450-350 B.C. 21 Although ascribed to the great physician Hippocrates of Cos, they are a most contradictory set of writings, some upholding the application of philosophical ideas in medicine, though with varying emphasis on specific philosophies, some specifically denying to philosophy any

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Development of Biochemical Concepts

place in medicine, and many being of a purely clinical character. They probably formed the library of a school of medicine, possibly that of Cos itself. 22 They were finally put together in the great Library at Alexandria in the Hellenistic period. T h e books well illustrate the varied approaches which were possible when physicians or philosophers interested in medicine tried to apply the theories of their predecessors to the mechanisms of bodily function. In some cases there can be no quarrel with the scientific attitude of the writers. The superstitious and mystical ideas which were found in some phases of Greek medicine received no support from the authors of such works as "The Sacred Disease" or "Ancient Medicine." T h e first of these, a discussion of epilepsy, expressly denied that this disease had a sacred or divine origin. Epilepsy was a disease like any other, and its cause was to be sought and its treatment carried out like that of any ordinary disease treated by the physician. This work is one of the great monuments to rational thinking in medicine. T h e second work, "Ancient Medicine," 23 is basically an attack on the Sicilian school of medicine of Empedocles, which emphasized fire, or heat, as the main cause of health and disease. The author of this treatise expressly denies that a preponderance or deficit of any single substance, whether heat or moisture, can cause all diseases. He reverts to the ideas of Alkmaion when he says "for there is in man salt and bitter, sweet and acid, astringent and insipid, and a vast number of other things possessing properties of all sorts, both in number and in strength. These, when mixed and compounded with one another, are neither apparent, nor do they hurt a man, but when one of them is separated off and stands alone, then it is apparent and hurts a man." 24 T h e proper treatment for such unbalances is by diet, and the treatise devotes much attention to the foods which are appropriate in various types of illness. This attention to diet was an important characteristic of Coan medicine in all cases. Although "Ancient Medicine" attacks the school of Empedocles, another Hippocratic work, "The Nature of Man," is strongly Empedoclean in its ideas. T h e work is particularly important, since it introduces for the first time the doctrine of the four

Classical Greece

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humors. Empedocles had established the four corporeal roots, earth, air, water, and fire, but these material substances were not unique to the living body. They were the roots of everything. T h e author of "The Nature of Man" equated these with the body fluids: "The body of man has in itself blood, phlegm, yellow bile, and black bile; these make up the nature of his body and through these he feels pain or enjoys health. Now he enjoys the most perfect health when these elements are duly proportioned to one another in respect of compounding, power, and bulk when they are perfectly mingled. Pain is felt when one of these elements is in deficit or excess, or is isolated in the body without being compounded with all the others. For when an element is isolated and stands by itself, not only must the place which it left become diseased, but the place where it stands in flood must, because of the excess, cause pain and distress." 25 Although these humors are body fluids, they partake of the nature of the Empedoclean roots: phlegm is the coldest con-· stituent of the body and so predominates in winter. Blood, associated with spring, is moist and warm; summer, dry and warm, is akin to yellow bile; and autumn, dry and cold, is associated with black bile. T h e humors thus fluctuate with the season, and each season has its characteristic illness for this reason. Once again, these diseases are to be treated by an appropriate diet. T h e treatise "Regimen in Health" is a detailed account of the manner in which different individuals should eat and exercise to keep the four humors in balance. However, the direct relation of the four humors to the four elements or, as yet, to the temperaments does not occur in the Hippocratic Corpus. 26 Other works in the Corpus are based on the theories of Heraklitos. This is particularly the case with the rather obscurely written treatise "On Nutriment." In this work the idea of constant change finds its application in the theory that fire and water, the components of the body, contend for mastery and in turn dominate the body. Health depends on a blending of these two components. 27 Food dissolves in moisture and is carried to every part of the body. Although food itself is "one" it is assimilated to the "many" parts of the body—bones, flesh, fat, and so on—as it encounters them. T h e air we breathe is also considered to be a food. T h e

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Development of Biochemical Concepts

author stresses the relativity of the effect of food: what is good for one man may not be good for another. He said: "All things are good or bad relatively." 28 Oddly enough, he considered that "milk and blood are what is left over from nutriment. 29 Another Heraklitean work is "Regimen," which contains a lengthy discussion of the effects of imbalance of fire and water. Fire is hot and dry, water is cold and moist, and their balance in the body constantly changes. These effects are compared to men sawing a log—one pushes, the other pulls, though the result is the same. 30 The structure of the body comes from food by mechanisms which explain in more detail the ideas expressed in "On Nutriment." Thus, food and breath by movement and the action of fire are dried and solidified, hardening around the outside. This traps the fire inside, and no more nourishment can be drawn in, while breath cannot be expelled through the hard outer layer. T h e available inner moisture is consumed; the interior parts become compacted and solid, and, in fact, become bones and sinews. In softer tissues the fire which is enclosed can break out, leaving passages for the breath and to supply nourishment. These are the hollow veins. Between these, what is left over from the water becomes compact and is converted to flesh. 31 T h e foregoing is an excellent example of the use of the philosophical theory of the author to account for specific biochemical facts. These ideas are extended to all spheres of life. Growing creatures have more innate heat, while older creatures have little.32 Females incline to water and grow from foods which are cold, moist, and gentle. Males, inclining to fire, grow from foods that are dry and warm. Thus if a man wishes to beget a girl, he must use a regimen inclining to water; if a boy, one inclining to fire. 33 An even more fundamental application of the theory is found in the discussion of intelligence in the soul. T h e greatest intelligence comes from a union of the moistest fire and the driest water for thus the most complete blending can occur. 34 A clinical description in this treatise tells of lowered intelligence when there is less heat in the body. It is a recognizable description of a hypothyroid individual. 35 Still another explanation of the physiology of man is found in the work entitled "Breaths." This is based fundamentally on the

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ideas of Anaximenes about the importance of air and respiration for life. T h e s e ideas had been made into a system by Diogenes of Apollonia (fl. about 430 B.C.), and it is his theory that is followed in "Breaths." T h e cause of all disease is ascribed to the air taken into the body, and much ingenuity is e x p e n d e d in explaining the exact mechanisms involved. It can be seen f r o m the foregoing that Greek physicians used many theories to explain the clinical and biological facts they observed, yet in almost every case they stressed the importance of blending a series of opposite qualities, substances, or humors. Such blending was to some extent analogous to digestion, and represented what we today would regard as a cherqical reaction. This process was called pepsis, which has been translated as "coction" or "concoction." It was the method by which the diverse elements in the food or in the body were brought into the intimate blending required for normal functioning of the body for perfect health. Jones has described it as "action which so combines the opposing h u m o r s that there results a perfect fusion of them all. No one is left in excess so as to cause trouble or pain to the individual." 3 6 Coction occurs normally at all times in the body. It is produced by heat and usually results in a thickening of the body fluids. In illness, coction is imperfect and fluids become thinner. Thus, in colds, the discharge f r o m the nose is at first thin and acrid, but when correct coction begins, the " r u n n i n g becomes thicker and less acrid, being m a t u r e d and more mixed than it was before." Finally it stops. In serious illness, the restoration of coction was believed to occur at the crisis, which took place on certain specified days of the disease. At this time either correct coction began and the patient recovered, or it did not and he died. This was a characteristic Hippocratic doctrine. T h e theoretical ideas expressed in the Hippocratic Corpus have been discussed at some length because they show the intense Greek e f f o r t to explain all the observed facts and to find mechanisms for all processes, but to be quite satisfied with these explanations when they were plausible and logical, without being concerned with proofs. T h e theories of the Hippocratic Corpus were based on various philosophical ideas and they involved d i f f e r e n t

16

Development of Biochemical Concepts

mechanisms to explain the same facts, but they were all essentially nonvitalistic. T h e f u n d a m e n t a l structures in the macrocosm and the microcosm were the same, and theories which explained one also explained the other. T h e s e theories were materialistic and mechanistic. Nevertheless, there was a more mystical school of philosophy in classical Greece—the sect of Pythagoras, which was mentioned above in connection with the ideas of Alkmaion. This sect or school continued to develop as the exponent of the conservative, antimaterialistic phase of Greek philosophy. T o it only the soul (psyche) was important; matter was merely the prison of the soul. This was a concept entirely distinct f r o m those of the philosophers and physicians thus far discussed, to whom the soul was simply "the innate capacity of bodies for change and movement." 3 7 T h e Pythagoreans did not desire to observe scientifically, as did the writers of the Hippocratic Corpus. Instead they wished to emphasize that aspect of Greek thought which dealt with moral, ethical, and social problems in the light of logic and reason. Contempt for the craftsman was strong in these thinkers. It was f r o m these m e n that Plato took many of his ideas. T h e r e is little of scientific or biological interest in most of Plato's writings, yet his influence on the development of science has been p r o f o u n d . What he did write of a scientific n a t u r e marked a turning point in Greek science, and his one scientific dialogue, the Timaeus, was available to Western m e n of learning t h r o u g h o u t most of the so-called dark ages. It represented to t h e m the f o u n d ation u p o n which they could base their scientific thinking. Although in this dialogue Plato is explicitly descending f r o m the heights of his ethical and moral discussions, he is doing so for the p u r p o s e of showing the necessity for o r d e r and good in the cosmos. H e is using the microcosm as he conceives it to show the p u r p o s e of the macrocosm. Nevertheless he is enough a Greek philosopher to wish to account for all the p h e n o m e n a he is discussing, and so, on the basis of ideas which he says are "as likely as any other," he gives a detailed account of the universe and man. T h e major difference between the ideas of Plato and those of the philosophers previously discussed lies in his teleology. T o

Classical Greece

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Plato, everything that exists was created and designed in the most perfect and beautiful form possible. T h e "Demiurge" who constructed the microcosm designed each step with the whole in mind, and nothing was done without a purpose. No false or useless steps were involved. Therefore everything which exists must exist to fulfill the purpose of the best of all possible worlds. Using this as his guiding principle, Plato shows in the Timaeus how the microcosm was created and functions. Then, in great detail he demonstrates how this microcosm, man, also shows the purpose of his creator. Plato had in common with his predecessors the desire to explain function; only his idea of purpose was different. He conceived of a variety of souls. T h e immortal soul, reason, was located in the brain and was well separated from the mortal soul in the trunk. T h e mortal soul had two parts, divided, according to his teleology, into a "higher" inferior soul, located in the chest and controlled by the heart, and a "lower" soul in the area below the midriff which controlled the appetites. The heart, a seat of heat and passion, was surrounded by the lungs to cool it. Each major organ of the body was assigned its position in terms of the effect which that position had on the other organs to keep man at his best and noblest. Plato's teleology can be illustrated by his explanation of the functions of respiration and digestion. Respiration takes place "in order that the body, being watered and cooled, may receive nourishment and life; for when the respiration is going in and out, and the fire, which is fast bound within, follows it, and ever and anon moving to and fro, enters the belly and reaches the meat and drink, it dissolves them, and, dividing them into small portions and guiding them through the passages where it goes, pumps them as from a fountain into channels of the veins, and makes the stream of the veins flow through the body as through a conduit." 38 Disease to Plato, as to the other philosophers, came from an unnatural excess or deficit of a substance, in this case, earth, air, fire, or water. T h u s Plato envisaged an overall purpose to which all things must conform, but he used mechanistic explanations to show how this purpose was carried out. Although in the Timaeus he devoted much space to his anatomical and physiological

18

Development of Biochemical Concepts

mechanisms, he was really interested in these only as they could be applied in the moral and ethical sphere. His introduction of the teleological concept t u r n e d Greek philosophy aside f r o m the path of the m o d e r n scientist. It has been said that this is the cause of the failure of Greek science to develop. 3 9 Nevertheless it was the teleological approach that m a d e so much of Plato and Aristotle acceptable to medieval m e n of learning. Plato's great pupil, Aristotle, was influenced by different aims. Although he took all knowledge for his field and wrote widely on social, political, and ethical questions, he was at heart a biologist, and some of his most ingenious work was d o n e in the field of zoology. His powers of observation were p r o f o u n d , and he was particularly f o n d of systematic classification. These traits are clearly shown in his "History of Animals," in which he presents a very complex classification of all the animal kingdom on the basis of his own observations in comparative anatomy. 4 0 However, it is in his other biological works, especially the "Parts of Animals" and "On Generation of Animals," that he develops the ideas which today would be considered biochemical. His idea of the cause of chemical reactions in the body is essentially that of the Hippocratic Corpus. T h e chief action is d u e to pepsis or coction, b r o u g h t about by inner heat, though he classifies various types of coction more fully than did his predecessors. In the work which has been called the first textbook of chemistry, 41 the f o u r t h book of the "Meteorologica, 4 2 he defines pepsis as "a complete transformation of a substance into a state of perfection f r o m one of the two passive qualities, the Dry and the Moist, being the p r o p e r matter of any given subject, to the opposite quality, b r o u g h t about by the peculiar inner heat." Pepsis ripens or transforms a body into the p r o p e r condition and thus converts it to something which can be used for a definite purpose. When the body is healthy, pepsis is occurring normally within it. Various ways of applying heat outside the body, such as broiling or boiling, produce modified types of pepsis.43 In this treatise there is an extensive explanation of the m a n n e r in which the combination of Aristotle's f o u r elements, the familiar heat, cold, moisture, and dryness, give characteristic physical properties to a large n u m b e r of substances. T h e application of these ideas to biological works is also extensive. 44

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19

Although Aristotle was far more scientifically minded than was Plato, and though he founded his biological ideas on very keen observation, he nevertheless accepted Plato's teleology completely. This is shown in the elaborate classification of causes by which he explained almost all the theories which he developed. He considered that there were four causes for any action or process. The most important was the final cause, the reason why the process took place. This was teleology at its most extreme. The other causes were the efficient, the formal, and the material. The efficient cause was the agent which set the process in motion, the formal cause gave form to the process, and the material cause was the substance on which the process took place. To use one of his examples, when a carpenter makes a chair, the final cause toward which everything works is the production of the chair. The efficient cause is the carpenter himself, who initiates the movements required to realize this purpose. His tools by which he carries out the process are the formal cause, and the wood of which the chair is made is the material cause. 45 Applied to such a process as making a chair, these causes are easy to understand, but Aristotle applied the same reasoning much more subtly in devising his theories of animal generation and behavior. 46 Of course, in all cases the final cause was the most important. To Aristotle, as to Plato, a process occurred because it was drawn forward from its end rather than pushed onward from the beginning, as a modern scientist would be more likely to picture it. 47 He also tended to regard the organism as a whole rather than considering it as a mass of separate parts. 48 This teleological viewpoint naturally colored his ideas of structure and function in the animal body. He said, for instance, that nature creates nothing without a purpose, but what she creates is always the best possible of its kind for the particular living creature to satisfy its needs. Thus, if one way is better than another, that is the way of nature. 49 Obviously, then, no animal will have superfluous parts to carry out the same function, but every part must have a use. 50 Although in the Aristotelian system the basic elements of which everything is made are the four qualities heat, cold, moisture, and dryness, Aristotle recognized that these were too minute and abstract for everyday use, and so he conceived of a second degree

20

Development of Biochemical Concepts

of composition in which the primary elements built up the homogeneous parts of animals, such as the bones and the flesh. In turn, these made u p the third and last stage of composition, the heterogeneous parts, such as faces or hands. 51 The homogeneous parts existed for the sake of the heterogeneous ones which carried on the operations of the body. However, the living body obviously possessed something to which it owed its vital character, for a corpse contains the same elements, but is not a man. The distinctive feature of the living being was the soul. As has been seen, this term was used in various ways by the Greeks. T h e mechanistic philosophers merely used it as a term for the processes of life. T o Plato it was the ultimate purpose of the body and was divided into higher and lower forms. This concept Aristotle took over, but, as usual, he introduced a more exact classification of the types of soul than had his teacher. He conceived of the soul as noncorporeal but existing at various levels. T h e lowest form was the nutritive soul, which was involved in the processes of utilization of food and of reproduction. Since these processes are common to all living beings, plants and animals alike possess the nutritive soul and under its influence carry out the basic processes without which life could not exist. Animals, however, have powers which plants do not possess, and so in animals we find the sentient soul, by which they experience sensation, as well as the appetitive and locomotive soul, by which they experience appetities and can move. Finally, the highest soul of all, possessed only by man, is the rational soul, which confers the gift of reason on man alone. Although Aristotle distinguished these souls and the powers they conferred carefully, he made it plain that they could not be separated from each other or from their possessors. 52 T h e soul signified both the function of the organisms and their capacities for function. 53 Although the soul was noncorporeal, it often operated through a corporeal agent, the connate pneuma. 5 4 This was a subtle kind of matter, present in the living being from the moment of conception until death. At times Aristotle seemed to think of it almost as a separate element, analogous to the fifth element or quintessence, the material of which the stars were made in the macrocosm. Similarly in the microcosm there was a matter above the

Classical Greece

21

ordinary elements which gave to life its properties. This was the Aristotelean interpretation of the air of Anaximenes, which had been accepted in one form or another as a feature of life by most Greek philosophers and was to play an important part in the thinking of most of the later Hellenistic philosophers as well. When Aristotle turned to the actual mechanisms of the animal organism, he made practical use of the rather abstract ideas which have been described. He believed that fertilization occurred when the semen of the male mixed with the menstrual blood of the female. In this case his causes were definitely involved. T h e final cause was, of course, the production of a new individual. T h e efficient cause, or agent, was the soul of the male, which was present in the semen. T h e material cause was the menstrual blood which furnished the material out of which the embryo was produced. T h e efficient cause, the male soul, carried the "movements" needed to begin the process of growth of the embryo, but the formal cause, the instrument, was the connate pneuma, which conferred life. 55 The male, to Aristotle as to the authors of the Hippocratic Corpus, naturally contained more heat than the female. The generative fluids, male and female, were produced from the nutriment of animals by coction due to innate heat. Since the male was naturally the possessor of more innate heat, the semen was more fully concocted than the menstrual blood (hence it no longer resembled blood), while the menstrual blood from the cooler female was less completely concocted. This did not mean that it had not undergone coction. It had, but it had not been able to attain the higher stages of the soul. It did not reach beyond the nutritive soul. Therefore, by itself it could not produce a living being. The function of the semen, fully concocted and so containing all the souls, was to supply "that which generates," that is, the activating principle. Aristotle did not believe that the semen contributed anything material to the embryo. T h e female supplied all the material through the menstrual blood. In making this point clear, Aristotle used an analogy which reminds the modern reader of the concept of enzymes, though of course Aristotle himself had no such idea. He compared fertilization to the coagulation of milk by the addi-

22

Development of Biochemical Concepts

tion of fig juice or rennet, the milk being the material and the fig juice or rennet the curdling principle which contributes nothing material to the milk. 56 Even the physical properties of semen showed its power. It was a compound of the pneuma, the spirit which contained the heat, and of water, and it could not freeze because air could not freeze. 57 It is of some interest that Aristotle believed the male did not actually need the testes, since he was unable to find these organs in all the animals he studied, though he was well aware of the physical changes produced by castration. 58 The developing embryo received its nourishment through the umbilical cord from the blood of the mother. 59 Nourishment of the infant came from milk, which was concocted blood and had the same nature for each animal as the secretion from which that animal was formed. 6 0 Growth was dependent upon nutriment and occurred when heat acted on food, concocting it. The mouth facilitated coction by breaking up the chewed food so that heat could act upon it in the upper and lower abdominal cavities, the stomach and large intestine. These cavities served as a sort of manger, holding the concocted food. Plants obtained food which had already been concocted in the earth, absorbing it through their roots. In animals the stomach was an internal substitute for earth. T h e blood vessels around the stomach acted like the roots of plants, absorbing the concocted nutriment into the body through the blood, which acted as the transporting agent. 61 Blood varied in character with the heat it contained. Thicker and hotter blood made for strength, thinner and colder blood for intelligence. The most intelligent animals had thin, cold blood, but those with hot blood which was also thin and clear had both courage and intelligence. Aristotle illustrated these statements with somewhat fanciful descriptions of the blood of various animals. 62 Blood consisted of a watery part which never coagulated and an earthy part which solidified when the watery part evaporated. Coagulation of blood when it was shed was due to the fact that it lost its heat and became cold. T h e most honorable portion of the nutriment, that which was most fully concocted, was used to form the sense organs, including flesh, which was considered a sense organ because it had the

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sense of touch. All other parts of the body existed for the sake of the flesh. The large blood vessels which carried nutriment from the stomach remained open and clear, but the smaller ones became clogged with flesh as the blood in them formed it, and so they could not be seen. However, when the flesh was cut it bled because they were still there. 63 When there was an abundance of nutriment, the excess over that which formed flesh was converted to fat, which might be either hard or soft as the composition of the blood varied. Too much fat was harmful, since it used up valuable materials which would otherwise have formed useful substances. 64 The inferior portions of nutriment served to form the lesser parts of the body, for nature throws nothing away which can possibly be made useful. Thus the residues of nutriment formed bones, sinews, hair, nails, and hoofs, which were the last to form because they had to wait for the left-over nutriment to become available.65 The dregs of solid food might be used to form scales and feathers, and the final residues were discarded as feces, while the dregs of liquid food appeared as urine. Plants needed no excretory organs because their food was already concocted in the earth and so had no dregs. Marrow was of the nature of blood. It formed the spinal cord and the brain. T h e spinal cord was hot, but the brain was cold. Since the latter organ could be touched without sensation, it was not an organ of sense. Rather, as the largest cold organ in the body, its function was to counterbalance the heat of the rest of the body, especially of the heart, which was the main source of heat and hence of motion. The brain tempered the heat and seething of the heart. It was therefore next in importance to the heart among bodily organs and so was connected to the heart by its vascular covering. 66 It was located at the top of the body because heat ascends. Man stood erect because his heart furnished the most heat of any animal and so had to be cooled most efficiently. Hair on the head protected the brain from variations in heat. 67 Bones excelled in earthy character and existed in order to support flesh. The lungs cooled and tempered the heart. Liver and spleen helped to concoct food, since they were of a hot character.

24

Development of Biochemical Concepts

The kidney collected residual fluids and might contain much fat because of the residues which percolated into it and were there concocted by the residual heat of the kidney itself. 68 All these examples are clear evidence of Aristotle's teleological thinking. It is also interesting to note that he considered the bile to be a nonessential fluid, since not all animals he examined had a gall bladder. Bile was only a purifying excretion and could not be a cause of disease. 69 This is an example of Aristotle's use of a direct observation in comparative anatomy to deny a medical theory which was based on far less specific observations, and so illustrates his capacity for independent scientific reasoning. In the biological books of Aristotle we possess a clear and comprehensive illustration of the tendency of the Greek mind to explain practically everything which could be observed. Aristotle was a better observer and a clearer thinker than most of the other philosophers, and so had a' firmer base on which to build his theories, but he was guided by teleology and by the universal desire of the Greeks to explain everything in a logical manner, even if the facts were insufficient for a truly logical explanation. We must still admire the ability and the daring of his biological theories. For his day, his biochemistry was as complete as is ours in our own time.

3 The Hellenistic Period

Although Aristotle offered full explanations of the functioning of animal bodies, his theories were not universally accepted by other Greek thinkers and physicians. Owing to the lack of experimentally determined facts, it was still possible to utilize the philosophical theories of whatever school an individual followed to build pictures of mechanisms which differed in detail from those of other thinkers. Our knowledge of such theories is not great for the early Hellenistic period which followed the days of Aristotle, a period which saw the decline of Athens as a great intellectual center after the conquests of Alexander the Great. However, during this period the spirit of enquiry did not die out among the Greeks. Rather it spread to the new cities which arose in the Hellenistic world when Greek civilization broadened and came into contact with other peoples. T h e foremost center of intellectual life was now Alexandria in Egypt, though there were other cities nearly as important. 1 At Alexandria was established the Museum, the closest approach to a modern research center which existed in the ancient world. All branches of science were practiced in Alexandria, and practiced with a new spirit, for the appeal to experi-

26

Development of Biochemical Concepts

m e n t began here. Less, perhaps, is known of the work d o n e in the biological fields than in the physical sciences, but even h e r e we know of the work of such m e n as the great anatomists Herophilus and Erasistratus (fl. 290 B.C.), and the latter has long been known as a physiologist. T h e r e seems to be little doubt that Erasistratus was greatly interested in the mechanisms by which the body functions and that he was a strong a d h e r e n t of the tradition of Anaximenes, with its emphasis on the importance of air. He accepted the idea of a vacuum which many philosophers had denied, but it was a discontinuous vacuum in which innumerable minute empty spaces were interspersed with the atoms of the body. 2 He explained almost all physiological p h e n o m e n a in terms of the horror vacui, the abhorrence of nature for a vacuum. T h e spaces of the body were t h e r e f o r e not actually empty, but were filled with p n e u m a , to which he gave a place of first importance. P n e u m a was drawn into the body t h r o u g h the lungs f r o m the exterior. As the heart e x p a n d e d in diastole it created a vacuum which drew the p n e u m a into the left ventricle. From here p n e u m a was distributed to the body t h r o u g h the arteries which contained only p n e u m a and no blood. Since it could flow, p n e u m a had to have density. T h e heart was an unidirectional p u m p which forced the p n e u m a , now called "vital spirit", t h r o u g h o u t the body and into the nerves, which were holtow tubes conveying the p n e u m a to the brain. H e r e it was converted into "psychic pneuma." 3 T h e emphasis which Erasistratus placed on p n e u m a (air) led him to reject the importance of innate heat (fire), and so he denied the significance of such heat in the coction of digestion. Food, g r o u n d mechanically in the stomach and there mixed with p n e u m a f r o m the arteries, was carried to the liver and there changed to blood. Although he did not attach much importance to the humors, Erasistratus did admit that thickened h u m o r s might sometimes impede the flow of body fluids and could thus at times prevent the assimilation of foods and cause malnutrition. 4 T h e doctrines of Erasistratus were widely accepted, and by emphasizing the importance of the p n e u m a they tended to widen the gulf between those who accepted the prime importance of the p n e u m a and those who stressed the significance of innate heat.

T h e Hellenistic Period

27

T h e results of this cleavage can be seen in much of the subsequent physiological speculation, and in the rise of divergent medical sects. O u r knowledge of the biochemical theories which prevailed between the time of Aristotle and that of Galen was greatly extended by the discovery in L o n d o n in 1892 of a papyrus known as Anonymus Londinensis. 5 It seems to be a collection of notes by a medical student or students taken at lectures of several important teachers and t r a n s f e r r e d to one roll for the use of a practicing physician in about the second century A.D. T h e papyrus falls naturally into three parts. T h e first is merely a r o u g h series of definitions, evidently taken down by a student who did not always hear clearly some of the words of the lecturer. T h e second portion appears to be based on the book of a certain Menon, a student of Aristotle, who composed a work, the latrikia, which was a review of the medical theories of the third century B.C., and which is mentioned by Galen, though the work itself is now lost. T h e third part is a survey of the physiological a n d biochemical theories of a n u m b e r of physicians and philosophers f r o m the third century B.C. to about the beginning of o u r era. 6 T h e extract f r o m Menon shows clearly that the physicians of the immediate post-Aristotelian period were using chemical concepts to explain the etiology of disease. Although a n u m b e r of authors are cited, some of them known only t h r o u g h this work, there are only two theories of disease: the older view that it results f r o m a disturbance in the blending of the elements, and the other, that the residues f r o m food may cause illness. T h e latter view may have originated f r o m the emphasis which the Hippocratic physicians placed on diet in disease. T h e r e was a definite chemical causation in either theory, however. For example, a certain Thrasymachus of Sardis, not otherwise known, is said to have believed that excess of heat or cold changes blood into phlegm or bile or pus, which then, by the excess, produces disease. 7 O n the other hand, Herodicus of Cnidos is cited as declaring that when m e n take nutriment without previous exercise, it is not assimilated, but remains in the belly without being digested or altered, and then is converted into two liquids, one acid, the other bitter. T h e s e are carried by the blood to the heart

28

Development of Biochemical Concepts

and other organs and by their relative amounts and the organ which they affect produce various diseases. 8 Still other workers, influenced no doubt by the theories of Erasistratus and their extension by the Stoics (see below), believed that when the whole body breathes well and the breath passes unhindered, health results. 9 These medical theories are interesting, but the physiological theories discussed in the third part of the papyrus are still more interesting from the biochemical point of view. T h e writer is quite practical in his outlook and remarks, "Man is composed of soul and body. As there is no need to touch on it, I leave the discussion of the soul to others, but we must pay attention to the body, since medicine is chiefly concerned herewith." 10 T h e author is mainly concerned with digestion and absorption of nutriment and in emanations from or absorption through the pores of the body. Since he is reviewing the work of others, his own ideas are not very clear. Nutriment is taken into the mouth as "crude food" and is cut to pieces by the teeth. There is some absorption of crude food in the mouth, since we can taste it, but most of it goes to the stomach where a certain amount of crude food is also absorbed. Most of the food is changed here, however, undergoing digestion, which is "a change and grinding fine as an aid to seething, being a kind of division." T h e exact nature of this seething is not made clear. Digestion and absorption continue in the intestines; the nutriment dispersed here is absorbed either "through the pores around the intestines, or by the vessels which grow into them." There is some dispute as to whether the arteries can absorb nutriment, but the veins certainly can. T h e residue from food is excreted and eaten by other animals and birds. These in turn are eaten by men and so "the residues of men become once more their nutriment." Here is a crude realization of the occurrence of biological cycles.11 Not all the food is absorbed then, but only the nourishing part of it, for if we absorbed everything we would grow enormously. In addition to the "inferior and more sluggish" parts of the nutriment, which are excreted in the feces, there is an attraction by the bladder for the pungent and salty parts of the nutriment, and

T h e Hellenistic Period

29

these appear in the urine. 12 Finally, there is loss of nutriment by emanations.These play a considerable part in the thinking of the writer of Anonymus Londinensis. Emanations are given off by everything and account for odors and nutritive qualities. Fresh meat and bread are said to be heavier than the old or stale substances because the latter have lost weight by emanations, and are also less nutritious on this account. 13 In the body, emanations are produced by warmth and movement. Warmth carries away moisture, as is shown when water boils. Emanations occur continuously in the body. Breath supplies some of the material for this emanation, since it is inhaled cold and exhaled warm. However, nutriment furnishes the rest of the emanation. 14 In this connection the author describes a remarkably interesting experiment by Erasistratus. It is on this experiment that his reputation as an experimental physiologist largely rests today. He placed a bird, "or something of the sort" in a pot and weighed it. He kept it without food for some time, then weighed it with its excreta and showed that there was a loss in weight which he considered was due to emanations. 15 Here is the first description of a quantitative experiment in biochemistry and one which was not repeated until in the seventeenth century, the work of Sanctorius. Logically enough, the author of Anonymus Londinensis considers that if material can be lost from the body through the pores, material can also be absorbed through them. He tells how Democritus, after fasting for four days was near death, but when he was placed in a bakery where the fresh bread shed its steam over him, he inhaled the steam and recovered. 16 It is worth while to include this account, since up to now we have focused our attention chiefly on the ideas of the Greeks which have a bearing on our own concepts. It should never be forgotten how much speculation went on, and how much was accepted as fact which from our point of view was completely without foundation. While Aristotelian ideas became dominant in the thinking of Arab and medieval philosophers and scientists, there were other schools of Greek thought which sought to explain the nature of life in terms of their own theories. One such school was that of the Stoics, who continued the tradition of Anaximenes, Diogenes

30

Development of Biochemical Concepts

of Apollonia, the treatise "Breaths" of the Hippocratic Corpus, and the theories of Erasistratus. They stressed the fundamental nature of air (pneuma) as had Aristotle, but they came to attribute to it all the phenomena of life. It became the all-pervasive, but corporeal, soul. They visualized an elastic medium within the body which extended in a condition of tension to the surface, where it received sensations from the outside. These were transmitted by a series of waves analogous to waves in water (a simile which they first used) to the soul, and this responded by transmitting waves to the surface again. The most apt comparison was to a spider in the middle of a web who receives impulses along the threads from any point and then responds by going to the affected point. 17 T h e pneuma was composed of fire and air, and it was the relative proportions of these which gave it its characteristic properties.18 Poseidonius (c. 135-c.' 50 B.C.) combined the four elements in a psychophysical parallelism with the properties of both soul and body. Illness was due to excess of one of the four qualities, an excess of which could arise from an outside source such as breathing or nutrition. Emotions could also arise from such a preponderance of qualities: anger from excess heat, fear from cold, and so on. 19 This theory of the Stoics, based on the idea of a continuum, was eventually revived in the form of the all-pervasive ether by a number of seventeenth-century scientists.20 Another philosophical school was that of the Epicureans. They were fundamentally atomists, following the materialistic doctrine of Democritus as this had been extended to the whole field of philosophy by Epicurus. Although this school did not have as many followers as the Stoics, it had many adherents in the Hellenistic and Roman worlds, and it produced one of the great literary works of early science, the De Rerum Natura of the Roman poet Lucretius (c.l00-c.55 B.C.). In Lucretius we find the atomic theory extended to its utmost limits. Much of the work was an attempt to explain physical phenomena as the result of interaction of atoms continually moving in a void, but he did not neglect biological or even psychological phenomena in his all-embracing system. Most characteristic was his complete turning away from the teleology imposed by Plato and generally accepted by later philosophers:

The Hellenistic Period

31

In this context there is one illusion you must do your level best to escape—an error to guard against with all your foresight. You must not imagine that the bright orbs of our eyes were created purposely, so that we might be able to look before us; that our need to stride ahead determined our equipment with the pliant props of thigh and ankle, set in the firm foundation of our feet; that our arms were fitted to stout shoulders, and helpful hands attached at either side, in order that we might do what is needful to sustain life. T o interpret these or any other phenomena on these lines is perversely to turn the truth upside down. In fact, nothing in our bodies was born in order that we might be able to use it, but the thing born creates the use. There was no seeing before the eyes were born, no talking before the tongue was created. T h e origin of the tongue was far anterior to speech. The ears were created long before a sound was heard. All the limbs, I am well assured, existed before their use. They cannot, therefore, have grown for the sake of being used. 21 It is obvious that with such a viewpoint, a mechanical explanation of life was essential, and Lucretius expended much ingenuity in explaining how the behavior of atoms could account for all of its phenomena. He placed great emphasis on the idea of effluvia, mentioned above in connection with the account in Anonymus Londinensis. He even explained sight by a film of atoms thrown off by material objects and affecting the eyes. Variations in the taste of food were due to variations in the shape of atoms, which could enter pores of certain sizes and shapes in the mouth and produce characteristic flavors, while other shapes that could not enter these pores could not be tasted. Odors also came from effluvia whose atoms affected the pores in the nostrils. 22 This idea of the continuous exchange of matter in the form of atoms between an organism and its environment was an extension of the idea of Heraklitos of continuous change. By the renewal of atoms in the same individual nature builds one object from another. This atomic idea did not play an important part in philosophical or medical thinking until the Renaissance, but it never died out completely. 23 As Rome became the center of power in the Mediterranean world, the various schools of Greek medical thought, based on the philosophical ideas of the Greek physicians as modified at

32

Development of Biochemical Concepts

Alexandria, gradually shifted their base and became centered at Rome. By the time of the founding of the empire, medicine at Rome was in the hands of Greek physicians. These men had split into a number of sects, each basing its system of treatment on a different phase of Greek medical philosophy. Some physicians remained strict followers of Hippocrates and his palliative system of treatment, but others developed more rigid ideas. T h e Dogmatic School took its theories from Cos and Sicily; the Pneumatists, following the Stoics, ascribed all bodily processes to the ebb and flow of the pneuma in the body. T h e Methodists, followers of the physician Asclepiades of Bithynia (124 B.C.), based their ideas on the atomism of Democritus and attributed disease to a constricted or relaxed condition of the solid particles and the pores which separated them. This doctrine was known as solidism. T h e Empirical School, followers of the Alexandrian physicians, tried to avoid theory as much as possible and to rely on observations as the basis of treatment. Finally, the Eclectics took what they wished from the other schools. 24 In actual practice, most physicians, whatever their affiliation, were probably eclectics to a greater or lesser degree, but the greatest Eclectic and the man who had the greatest effect on later medicine, anatomy, physiology, and biochemisty was the Greek philosophical physician Galen of Pergamon (C.129-C.199 A.D.). In him we find the culmination of the development of Greek biology, and after him this development came to an abrupt halt. Galen is usually thought of as a great exponent of the doctrine of the four humors, stressing their connection with the temperaments. As has been seen, however, the idea of the humors was not original with him, nor did he name the temperamental types: sanguine, melancholic, choleric, and phlegmatic. These names were applied by Honorius of Autun in the twelfth century. 25 Galen has always been especially known for his emphasis on the use of drugs ("galenicals"). He classified drugs into four "degrees" of one or more of the qualities warm, cold, moist, and dry. T h u s a d r u g might be warm in the second degree and moist in the third. This gave him a rough idea of the type and severity of the disease which the d r u g might treat. 26 This is an early exampie of an attempt at quantification in medicine. 27 It has been sug-

T h e Hellenistic Period

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gested that he stressed pharmacology rather than diet as the Hippocratic physicians had d o n e because of the rapid increase in malaria a r o u n d the Mediterranean in his day and the need for treating it drastically. 28 However, most of his drugs were not original with him, n o r were they especially effective. 2 9 Galen's anatomical and physiological ideas, like most of his theories, were largely derived f r o m his predecessors, but he organized them in such a convincing m a n n e r that they became the basis for all medieval thinking on these subjects. Hence it is well to consider them in some detail. Basic to all his conceptions was the teleology of Plato and Aristotle. H e had no use for the Epicurean doctrines. In his opinion, the chief agent for carrying out changes in the body was innate heat. H e assigned a much less important place to the p n e u m a , and he attacked many of the views of Erasistratus with considerable vigor. Above all, however, he was an experimentalist. His studies of the anatomy and physiology of animals were extensive, though his interpretations of what he saw were often colored by his theoretical preconceptions. H e wrote incessantly, and the sheer volume of his works is impressive. T h e s e works are full of biochemical ideas. In the view of Galen, we cannot know the use of any organ in the body b e f o r e we know its function. 3 0 Also, he felt that "all the dispositions of N a t u r e are admirable." 3 1 T h e r e f o r e one of his longest works, On the Usefulness of the Parts of the Body,32 is a detailed discussion of why every organ of the body is placed where it is so that it can carry out best the work designed for it by Nature. It was his insistence on explaining function that led Galen to present so many mechanisms of a biochemical type. In his view, innate heat was essential to life, and this heat came originally f r o m food, which both nourished and heated the body. 3 3 Food taken into the m o u t h was changed into a new f o r m to some extent because of the phlegm (saliva) with which it came in contact, but it was less changed than in the stomach, where it came into contact with and was acted on by phlegm, bile, p n e u m a , and innate heat. 3 4 In the stomach it u n d e r w e n t a first elaboration, d u r i n g which the useless parts were separated. T h e useful parts then passed t h r o u g h the intestines and by way of the

34

Development of Biochemical Concepts

veins were carried to the liver. Water was required at all stages to transport solid material. In the liver there was a second elaboration, due to coction, by which food was converted into blood. Galen constantly used familiar illustrations to make his mechanisms clearer to the reader, and in this case he compared the processes of digestion to the handling of grain. Here the stomach was the granary in which the grain was stored and sorted, and the liver was the bakery in which the bread was finally made. 35 Inhaled air was digested in the lungs, just as was food in the liver, though little of it reached the heart. It imparted quality rather than substance to the body. 36 Blood was of fundamental importance to Galen. He showed by experimental ligation of a section of an artery that it contained blood and not pneuma, as Erasistratus had declared. T h e blood formed in the liver was "on the way" to becoming flesh, which was the highest form of assimilation of nutriment; but not all blood was the same. It underwent various degrees of coction and so varied in thickness and heat. Each type of blood nourished the organ most like it. T h e four humors which played such an important part in Galen's thinking were also formed from various types of blood. 37 Proper mixing of humors resulted in health; improper mixing, in disease. The purest form of blood was that charged with pneuma. 3 8 Pneuma in turn came from the lungs, but not all inhaled air was pneuma. In fact, most of the air served merely to cool the excess heat of the heart and was then breathed out again. However, the portion which was pneuma passed through the heart and mixed with the blood for the production of the essential innate heat. Galen was aware that flames could not exist without air, and he believed that innate heat was only produced by some kind of combustion. He drew the analogy of a lamp, comparing the heart to the wick, the blood to the oil, and the pneuma to the "quality" which produced the combustion. In addition, the heart served to eliminate some of the waste products which occurred in the blood as a "smoky mist." These passed out into the lungs and were exhaled. 39 T h e mechanism by which the various organs obtained the specific nutriment which they needed involved what Galen called

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35

the "natural faculties." He had been strongly impressed by the attraction which the lodestone exerted for iron, and he assumed that each bodily function was controlled by a similar sort of natural attraction, a given organ attracting that which it needed. H e did not entirely discard the idea of the horror vacui of Erasistratus, but he assigned it a very subordinate place in physiological mechanisms. Each organ thus contained a special attractive faculty and special alterative faculties, originally e n g e n d e r e d f r o m the menstrual blood of the mother. 4 0 T h e important faculties included the formative faculty, which shaped every part, "doing everything for some purpose so that there is nothing ineffective or superfluous or capable of being better disposed"; 4 1 the growth faculty, which predominated in childhood and for which nutrients were needed; the alterative faculty, which introduced something which was not there before; and the nutritive faculty, which produced the assimilation of nutrients. Nutrition actually took place because of attraction or assimilation of that which nourished to that which received nourishment. Assimilation was preceded by adhesion, and this in t u r n by presentation, the latter stage being the goal of the activity which corresponded to the attractive faculty. This b r o u g h t the food f r o m the veins to the part which was to be nourished. A retentive faculty held the food in place until nourishment was complete. 4 2 Galen demonstrated that the stomach had a retentive faculty by an experiment with living pigs: "I gave [the pigs] a sort of mess of wheaten flour and water, and thereafter cutting t h e m open after three or f o u r hours; if you will d o this yourself, you will find the food still in the stomach. 4 3 T h e process of assimilation occurred in steps. "How would blood ever t u r n into bone without having become, as far as possible, thickened a n d white? And how could bread t u r n into blood without having gradually parted with its whiteness and acquired redness? T h u s it is quite easy for blood to become flesh, for if N a t u r e thickens it to such an extent that it acquires a certain consistency and ceases to be fluid, it thus becomes original, newly f o r m e d flesh, but in o r d e r that blood may t u r n into bone much time is needed and much elaboration and transformation of the blood. F u r t h e r it is quite clear that bread, and m o r e particularly

36

Development of Biochemical Concepts

lettuce, beet, and the like require a great deal of alteration to become blood." This is why many organs are needed to alter food. 44 Each organ has its attractive faculty: kidney for urine, stomach for nutrients, and gallbladder for yellow bile, among others. There is an "inborn faculty given by Nature to each one of the organs at the very beginning." 45 The doctrine of faculties has been criticized for not really explaining the causes of the actions ascribed to the separate faculties. However, as King has pointed out, 46 the doctrine was actually of considerable value. It brought together a number of separate processes and permitted a systematization not previously achieved. More importantly, it accounted for the specificity of action of individual organs in a system notable for the generality of its explanation of bodily processes. The importance of the idea of specificity was not otherwise stressed until the time of Paracelsus in the fifteenth century. As can be seen, the work of Galen sums up and summarizes the 700 years of development of Greek biology which extends from the time of Anaximenes in 550 B.C. Galen chose the elements of his system from the wide variety of speculations which revolved around the ideas of innate heat (fire), pneuma (air), and coction as the combining power, and he held them together with the basic principle of teleology. T h e teleological aspect, which appealed strongly to his Muslim and Christian successors, and the detailed logic of his presentation, in spite of the somewhat superficial nature of some of his ideas, made him the model physician for all the centuries until the days of Paracelsus.

4 The Early Middle Ages

T h e decline of creative medical theorizing after the time of Galen was only a reflection of the general decline of scientific interest throughout the Hellenistic world. The increasing influence of the mystical eastern religions, the Gnostic and Neoplatonic philosophies, and the eventual triumph of Christianity all combined to stress the importance of revelation instead of observation for obtaining an understanding of the nature of the world. Men who in earlier times might have devoted themselves to philosophy or science turned their attention to theology. 1 Those who still considered themselves philosophers spent most of their time in organizing the literature which had come down to them. T h e synthetic approach by which the specialists in each field tried to summarize all the work on a given subject found supreme expression in the masterworks of Euclid, Ptolemy, and Galen in geometry, astronomy, and medicine, but the compilation of handbooks in every scientific field was also carried on by many lesser men. This activity coincided with the period in which Rome was assuming political dominance over the Hellenistic world. T h e Romans admired the Greek intellect and tried to take Greek

38

D e v e l o p m e n t of Biochemical Concepts

philosophy back to R o m e . However, the d i f f e r e n c e s in outlook a n d interest inevitably resulted in a selective choice of the elem e n t s of G r e e k philosophy that would be m o r e congenial to the R o m a n s . T h i s was particularly t r u e of Greek science. T h e R o m a n s were a f a r m o r e practical people t h a n t h e Greeks a n d w e r e little interested in the abstract philosophical speculations in which t h e G r e e k thinkers delighted. Fortunately, f r o m the R o m a n point of view, t h e h a n d b o o k s which the A l e x a n d r i a n scholars were compiling contained j u s t t h e practical i n f o r m a t i o n t h e R o m a n s desired. 2 I n addition to these h a n d b o o k s , R o m a n s were also f o n d of large encyclopedic works which discussed all fields of knowledge. Many of the best-known n a m e s in R o m a n science a r e those of encyclopedists. Obviously these m e n could not have h a d first-hand acquaintance with everything they included in their compilations. T h e r e f o r e they d r e w heavily o n all available sources: G r e e k science plus folk tales a n d mythological stories, which they b l e n d e d t o g e t h e r in a r a t h e r uncritical h o d g e - p o d g e . H a n d b o o k s a n d encyclopedic compilations were thus the characteristic f o r m s of scientific writing a m o n g the classical Italian authors, a n d it was particularly t h e encyclopedia which f o r m e d t h e basis f o r the science of western E u r o p e d u r i n g t h e M i d d l e Ages. Actually, in speaking of the Middle Ages it is necessary to distinguish between the western states, which owed their culture to Rome, a n d the eastern e m p i r e , w h e r e t h e G r e e k l a n g u a g e a n d some of t h e traditions still survived. A f t e r the separation of t h e R o m a n E m p i r e in t h e time of C o n s t a n t i n e (c.288-337) knowledge of Greek declined steadily in the west, so that only Latin a u t h o r s could be r e a d by most e d u c a t e d m e n . T h e strong political divergence between R o m e a n d Constantinople, o r Byzantium as it c a m e to be called, was reflected in a n equal intellectual divergence. T h u s , in tracing t h e course of biochemical concepts it is necessary to follow t h e m separately in t h e two g e o g r a p h i c areas. O n e of t h e most influential early R o m a n encyclopedists was Marcus T e r e n t i u s V a r r o (116-27 B.C.) whose Nine Books of Disciplines set a p a t t e r n that was to be followed t h r o u g h t h e western medieval world. T h e book itself is lost, b u t its contents are k n o w n to us f r o m the n u m e r o u s citations to it by later writers. 3 V a r r o chose seven philosophical disciplines as the basis f o r a liberal

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education: grammar, dialectic, and rhetoric (later known as the trivium), and geometry, arithmetic, astronomy, and music (later the quadrivium). To these Varro added the more practical arts of architecture and medicine. These two subjects were later treated in special books, such as those of Vitruvius on architecture and Celsus on medicine. They thus tended to become independent disciplines. When Martianus Capella (fifth century A.D.) set the pattern of the medieval liberal education by making the formal separation of the trivium and the quadrivium, he excluded the two practical arts from the field of general learning, for these were no longer considered a part of philosophy. 4 Medicine was thus essentially a practical art, and physicians once more became for the most part leeches. Yet the philosophical approach was not entirely abandoned. Chalcidius (fourth century A.D.) had made a partial translation of Plato's Timaeus into Latin, and this remained the source of all medieval knowledge of Plato, including his physiological speculations. 5 T h e writings of Aristotle known to the west were his logical works as translated by Boethius (c.480-524).6 There was little of medical interest in these. A few encyclopedists attempted to carry on the Roman tradition without access to any of the original Greek sources, and they managed to gather at least some information about most subjects, including medicine. Among the more influential of such encyclopedists was Isadore of Seville (c.570-636), whose Etymologia was designed as a compendium of all knowledge. 7 In it he included some physiological speculation, founded essentially on the ideas of Galen. These were much simplified, however, and in the majority of cases were subordinated to the moral and theological portions of the book. 8 T h e heart was described as the seat of the pneuma and was the organ which set it in motion. T h e material heat of the liver converted food into blood. However, it was not only physical change which occurred in the organs. Emotions also centered there. We laugh with the spleen, are angry with the bile, understand with the heart, and love with the liver.9 T h e fundamental ideas of Greek medicine still prevailed. Balance of the four humors was the cause of health, their imbalance the cause of disease. 10 Beyond these simple concepts Isadore did not go.

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Development of Biochemical Concepts

T h e purely medical works of this period, as distinct from philosophical and encyclopedic writings, grew more and more practical with the passage of time. There was some attempt to translate a few of the Hippocratic and Galenic works in the sixth century medical school in Ravenna, 11 but most writers were content to describe diseases and drugs. An influential example of this class of writings is the long medical poem composed by Benedictus Crispus about 680. 12 This was based chiefly on a similar poem by a certain Serenus probably written in the third century, and on Pliny. Neither of these sources included a discussion of Greek philosophical medicine. Hence the poem of Crispus contains no mention of the humors and temperaments. It is essentially a list of diseases, their symptoms, and the drugs to be used in treating them. This was the type of handbook available to western physicians in the Middle Ages. If the ideas of the Greeks had not been continued elsewhere, their theory of medicine would have had to be rediscovered. However, in the eastern half of the empire Greek concepts of medicine and biochemical ideas were not lost, and could eventually return to the west when the climate was more favorable to them. T h e Hellenistic traditions were continued in the schools of Athens and Alexandria, which continued to function at least until the seventh century. Greek was the language of the eastern empire. Therefore the original writing of the Greek philosophers continued to be understood and discussed. Handbooks were written and larger syntheses were at times attempted even by Christian clerics. At the end of the fourth century Nemesius, Bishop of Emesa in Syria, composed a work, On the Nature of Man, in which he used the theories of Galen on the production of vital heat. Nemesius said: "So long as the heart is hot, just as long is the whole living body heated." 13 However, the characteristic form of scientific writing became the commentary, in which the works of the great predecessors were discussed and interpreted. Sometimes new and original contributions were made by the commentators. It is true that in later centuries, especially in Byzantium, the commentaries often

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became mere scholastic exercises, but the original texts were still preserved. Medicine remained a part of philosophy much longer in the east than in the west. Therefore the theoretical aspects stressed by Galen continued to be taught. At the same time, a new practical science began to develop in Alexandria. This was alchemy, which, whatever its later aberrations, was in fact at first a true, applied science. 14 It arose in the first century A.D. by combining the empirical observations of the Egyptian metal workers with the cosmological speculations of Greek philosophy. The metal workers were accustomed to see the properties and changes of metals during the manufacture of gold, silver, copper, and other metallic vessels, and the behavior of the various chemicals they used in their work. They soon noted that these changes could be explained in terms of Greek scientific theory. In particular, they accepted Aristotelian ideas to explain what they saw in their workshops. According to Aristotle, anything could be changed into anything else by altering the form impressed on a fundamental matter. Therefore, when these artisans produced an alloy from base metals of little value, which yet resembled the valuable and much desired gold, they saw no reason for not believing that they had succeeded in producing true gold. They also utilized the macrocosm-microcosm theory and compared the growth and perfection of plants and animals to the growth and perfection of metals in the earth. They sought to repeat such growth in their workshops. In the course of these activities they developed many processes and many types of apparatus in which to carry on these operations. Processes such as distillation, sublimation, and extraction were regularly carried out in specially designed pieces of apparatus. Inevitably the vitalistic ideas of the behavior of matter and practical laboratory operations which could easily be adapted for the preparation of drugs brought the alchemists into close contact with physicians. Thus began a long period of cooperation in which many of the physicians interested in developing a theory of medicine were also alchemists. It followed that men who worked with material substances and explained their results in material terms would also seek to explain vital bodily processes

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Development of Biochemical Concepts

in terms of material theory. T h e abstract ideas of the philosophers gradually became more concrete. Biochemical concepts grew more definite as time passed. 15 As noted above, medicine in the old tradition continued to be taught in Alexandria until well into the seventh century. T h e works of Galen formed the basis of medical teaching, and his authority remained unquestioned. 16 Medical students had to know philosophy as a basic part of their curriculum. T h e medical literature of the sixth century seems to be mostly in the form of lecture notes with a strong Neoplatonic tinge. 17 Gradually, however, the separation between philosophy and medicine became more pronounced. Philosophy ceased to be a paying profession among the intellectuals, and the thinking of practical physicians began to dominate medicine. 18 These physicians still drew upon the theories originated by the philosophers, but they also drew u p the practical knowledge of the leech and the alchemist. Thus, when the chief centers of medical instruction shifted from Alexandria, a new spirit animated both teachers and students. T h e role of Alexandria as a center of intellectual life declined steadily in importance after it was Christianized in the sixth century, and even more so after the conquest by the Persians in 617 and by the Arabs in 641. Meanwhile new centers were beginning to emerge. Antioch and Harran acquired much of the Alexandrian knowledge. 19 Even more significantly, the Nestorian Church broke from the Orthodox Church, which was favored in Byzantium, and established an important school at Edessa in Asia Minor. In 489 the school was moved in Nisibis in Persia. Here began the great series of translations of Greek scientific works into Syriac, the Semitic tongue of this part of the Persian empire. T h e Alexandrian medical and alchemical literature formed no small part of these translations. Very soon a Nestorian medical school was founded at Jundi Shapur, and it was from this center that the works of Galen and other medical writers reached the Arabs. 20 After the great Arab conquests of the seventh and eighth centuries, a brilliant scientific culture arose in the newly founded capital of Baghdad, which was located not far from Jundi Shapur. T h e Arabs not only received knowledge of the science and medicine of the Greeks from this source, but also, because of their

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geographic location, were favorably situated to receive ideas from India and even from farther to the east, from China. Each of these cultures had developed complex and characteristic philosophies, and, like the Greeks, had based their medical theories on their philosophies. T h e intermediately placed Arabs took elements from all three of these cultures and in turn passed on their version to western Europe. Therefore it is necessary to consider the development of biochemical concepts in India and China.

5 Chinese and Indian Concepts

As in Greece, biology in China was Firmly grounded in philosophy. In early China there were three main schools of philosophy: Confucianism, Buddhism, and Taoism. Though in their later development these acquired the aspects of religions, they always had stronger philosophical roots than western religions. The Confucians were largely concerned with man's ethical relationships and with proper government of state and family. Buddhism was imported from India and chiefly dealt with the mystical development of the human soul. Taoism began as an abstruse and almost mystical attempt to find the Way by which man could conform to Nature and thus live in harmony with the world around him. Tao means way, or path, and came to mean the Way of Nature. Lao Tzu (4th century B.C.), 1 the founder of Taoism, was the author of the Tao Te Ching, a highly abstract and poetical work which is one of the great classics of China. It was probably written shortly before 300 B.C. 2 However, Taoism did not remain an abstract philosophy for very long. If one seeks to conform to the Way of Nature, one must know what the Way is. In seeking this knowledge, the Taoist found an already established Nature Philosophy with complex but concrete cosmological explanations

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45

of the world, and he adapted these as his guide in the attempt to perfect his life. These cosmological theories were probably developed over a long period of time from the primitive mythology of the early Chinese, but they were organized and set down by Tsou Yen (c.350-c.270 B.C.) and the members of his Naturalist School. 3 T h e fundamental idea on which Chinese science was based was the principle of opposites, though it did not specify the large number of contraries enumerated by the Greek philosophers. All the contraries were summed up in the two great principles of Yang and Yin. Yang represented light, fire, maleness, and all active principles, while Yin stood for all that was dark, heavy, female, and passive. There was no moral sense in the opposites. They did not stand for good and evil as did the contraries of the Persians, Manicheans, and Christians. They stood rather for the forces of nature, and they were interrelated in a great cyclic scheme represented by the symbol which always stood for them. All nature operated in a wave-like succession: the dominance of Yang was followed by that of Yin, and this again by dominance of Yang. The material world was simply a reflection of this cyclic pattern. The behavior of things was inevitable in an ever-moving cyclic universe. In fact, the key to this concept lies in the word "pattern." T h e Tao, the Way of Nature, was dynamic; it proceeded on its own path, and if harmony was to prevail, this path had to be understood and followed. 4 Since everything in the world was related to this world pattern, it followed that living beings and the inorganic world were merely different manifestations of the same inevitability. Thus the macrocosm-microcosm theory was adhered to even more strongly by the Chinese than by the Greeks. 5 T h e operations of Yang and Yin were manifested in the relationship of the five elements: water, fire, wood, metal, and earth. These elements are not to be interpreted in the atomic sense of the Greek philosophers. Rather they were part of the cyclic interaction of Yang and Yin, each of the five acquiring dominance for a time and then passing into or producing the next of the five. Basically, they were not substances, but operations which produced properties in the physical world. 6 Almost all physical

46

Development of Biochemical Concepts

objects, together with their properties, could be classified into one of five categories related to the elements, and thus the number five became a characteristic of all Chinese scientific thought. There were five colors, five odors, five tastes, five directions, five major organs of the body, and so on in the great profusion. 7 In Chinese scientific theory everything was organized and interrelated and followed its inevitable patterned course. This was the Tao to which man should fit himself if he wished to lead a happy and productive life. The philosophy of Taoism began as an almost mystical attempt to conform to this Way. Originally this was to be achieved by withdrawing from active participation in worldly affairs, since these were the artificial doings of man alone and would probably be in violation of the pattern of Nature. Inactivity in the sense of avoiding such artificial violations was the goal of the early Taoists. However, man must also know how the Tao operates, and here the theories of the Naturalist School gave a concrete pattern to be studied. Nothing in the world was outside the scope of inquiry, no matter how repulsive or disagreeable it might seem. Everything should be studied objectively.8 Man could hold no special place in Nature, for he was a part of it. This left no room for the teleology of a Plato or a Galen. The world was not created for man, as the little Chinese boy pointed out. When his father exclaimed how good it was that heaven made excellent food for him, the boy remarked that man is stung by mosquitoes or eaten by tigers, but would one say that man was therefore created for the benefit of mosquitoes or tigers? 9 This rational and somewhat skeptical approach to Nature led many Taoists away from the abstract philosophy of Lao Tzu and to a more practical approach to the attainment of a satisfactory life. They believed that if man lived completely according to the Tao he could obtain all that was desirable. This included perpetual youth, health, and the possession of various supernatural powers. A person who had reached this state had attained "fullness of life" and had become a "true man," a Hsien. This term is usually translated as genii or immortal. T h e Chinese did not believe that they would attain the state of a Hsien by separation of the soul from the body. As part of the universal pattern of Nature, soul and body were one. There

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was no need to think of special souls to control bodily functions as the Greeks had done. 10 Instead man could become an immortal by acting on his physical body by physical means. Thus the seeker of immortality employed physical substances, either already part of his body, or added to it from the outer world, to bring about the desired condition. Biochemical concepts were clearly involved here. T h e actual methods used included special methods of breathing, exposure of the body to sunlight (for males) or to moonlight (for females), special gymnastic or sexual techniques, 11 and above all, alchemical procedures. T h e methods are described and evaluated in some detail in the Nei P'ien of the alchemist Ko Hung (c.280-c.340).12 As among the Greeks, breath was considered a vital essence. Therefore it was desirable to retain it in the body as long as possible, and Ko described various techniques for "circulating the breath" by holding it as long as possible and exhaling only in small quantities at a time. 13 When this art was learned and utilized, even poisonous snakes could not harm the adept. 14 T h e doctrine was further explained in medical terms: "There are six breaths in nature and they produce all savors, colors, and musical chords. Excess causes the illnesses. T h e six breaths are: yin, yang, wind, rain, darkness, and light. They are apportioned among the four seasons and arranged into the five musical chords. Excess on the part of any of the six breaths causes damage. Too much yin, there will be chills; too much yang, fever; too much wind, illness in the extremities; too much rain, digestive troubles; too much darkness, delusion; too much light, illness for the heart and mind." 15 Similarly, the semen was a vital fluid which, when retained in the body, could nourish the brain and increase vitality. Various techniques for sexual intercourse were therefore prescribed, designed to prevent as great a loss of semen as possible. 16 Finally, the taking of various medicines, both organic and inorganic, could lead to immortality. It seemed natural that the most perfect metal, gold, should be most effective in perfecting life. However, few seekers after hsienhood could afford much gold, and so the best procedure was to make it artificially. Alchemy probably began in China at an earlier date than in Alexandria. 17 Chinese alchemical literature abounds in stories of men and even dogs who consumed artificial gold and became

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Development of Biochemical Concepts

immortal. It has been pointed out, however, that the true adept did not always promise that the alchemist would live forever. He merely promised that he would never grow old. In many cases this was certainly true, since preparations of mercury salts were often the pill which the alchemist consumed. T h e fundamental difference between Chinese and Greek alchemy lay just in this search for a biologically effective agent. T h e Greek wanted gold for its own sake, and the Chinese for what it could do for his body. Thus from the beginning the latter was concerned with the functioning of that body. His strong belief in the macrocosm-microcosm theory and the perpetual interaction of the forces of Nature strengthened his tendency to consider the mechanism of bodily functions. To a degree even stronger than in the Greek-speaking west alchemical and medical theories tended to fuse, and alchemist and physician were often combined in the same individual. The philosophical background of Chinese biochemical concepts is very clearly revealed in the Huang Ti Nei Ching Su Wen, the Yellow Emperor's Classic of Internal Medicine, which is supposedly the oldest medical book extant. 18 This clearly shows how the cosmological theories of the Naturalists and the Taoists were used to present a truly biochemical picture of the functioning of the human body. According to this work, man is the product of heaven and earth, produced by the interaction of Yang and Yin and thus containing the five elements. These are each associated with a corresponding organ, season, climate, and so on. Liver is associated with wood and spring, heart with fire and summer, spleen with earth and late summer, lungs with metal and autumn, kidneys with water and winter. When these are in balance and succeed each other according to the Tao, health ensues. When they are in the wrong proportions, illness results. 19 In accord with Chinese thinking, the organs are described "for their function rather than location and structure, and the continuous interaction of Yang and Yin, the four seasons, and the five elements dominates the theory of structure as well as those of function." 20 Food which enters the stomach flows to the liver from which its vital forces ascend to the muscles while its gases pass to the heart, the origin of blood and animal heat. 21 T h e solid bulk of

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food descends from the liver to the anus. Similarly liquids go to the spleen which sends secretions to the lungs and from there to the bladder. Every part of the body is under the control of Yang and Yin, and there are a number of numerological relations, such as those between the number of days in the year and the number of bones in the body. There are twelve main ducts in the body through which Yang and Yin circulate and determine the content of the lesser vessels which are filled with air and blood. These ducts are connected by deeply embedded vessels which, however, come to the surface of the body at 360 specific points. It is the ebb and flow of Yang and Yin, succeeding each other like day and night, which keeps the body healthy. When this ebb and flow cease, stagnation occurs in the channels. Here the practical physician steps in. By puncturing the vessels at the specific points where they reach the surface, the stagnated air escapes, and health is restored. This is the classic Chinese method of treatment, acupuncture. T h e skilled physician knew where the specific stagnation occurred. He often learned this by an elaborate system of feeling the pulse. Then he could puncture the vessels at the proper points, using the proper kind of needle, and so could restore the patient to health. 22 Another characteristic feature of Chinese medicine was its reliance on herbal therapy. Plants were related through the five seasons, flavors, and climates to the five organs of the body, and so could be used to treat disorders of these organs. 23 Although most of the herbs were of little value, some actually contained potent pharmacological principles. Thus, ephedrine was first brought to the attention of western pharmacologists because of the effects of the Chinese herb which contained it.24 T h e Chinese physicians, operating on their philosophical theories, but accustomed to actual operations in their workshops, made observations at an early date which anticipated some of the discoveries of modern biochemistry. Night blindness, due to a vitamin A deficiency, was described early in the seventh century and was treated with pig and sheep livers.25 Between the tenth and sixteenth centuries methods were worked out for evaporating large amounts of urine, precipitating proteins with calcium sulfate or saponin, and leaching the precipitates with hot water. As a final

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step the p r o d u c t was sublimed. Careful attention was paid to technique t h r o u g h o u t . T h e product was used to treat hypogonadal conditions. Lu and N e e d h a m have pointed out that this p r o c e d u r e would give a c r u d e mixture of steroids. 26 T h e philosophical rationale of this method was that urine was of the same category as blood and so the virtues emanating f r o m the organs might be f o u n d in it. T h e r e was a continuous interaction a m o n g the organs of the body, mediated t h r o u g h the circulating blood. T h e civilization of India was geographically closer to the Arabs than was the Chinese, and so could have been expected to have reached the f o r m e r m o r e easily. It is extremely difficult, however, to identify the indigenous elements in Indian philosophy and the medical theories derived f r o m it. Certainly t h e r e are a n u m b e r of Indian ideas similar to those of China, and others close to Greek thought. Such similarities could well be expected, since contact with neighboring China was relatively easy, and direct contact with Greek culture occurred d u r i n g the conquests of Alexander the Great. Contact also occurred t h r o u g h Persia, where Greek physicians were employed over a long period of time. 2 7 A f u r t h e r difficulty in determining the origin of Indian theories lies in the fact that it is almost impossible to date the Indian manuscripts which have come down to us. T h e s e have usually been compiled f r o m much earlier materials. It is probable, however, that the old Vedic medicine, systematized a r o u n d 800 B.C., involved the use of both charms and drugs. 2 8 T h e r e was a rationale even in the employment of magic charms. T h u s , the yellow color chracteristic of jaundice was related to a specific yellow d e m o n , and the magical treatment was aimed at causing this d e m o n to ascend to the yellow sun, or to be t r a n s f e r r e d to yellow animals. 2 9 This idea could be extended to herbs. T h e s e were products of the earth a n d sky, that is, of the macrocosm, and so the macrocosm-microcosm theory was employed to suggest a p r o p e r use. 30 As Indian philosophy was systematized, the older forms of medicine gave way to a more philosophically based structure, Ayuraveda, the science of life, which was probably well organized by 400-300 B.C. 3 1 T h e clearest statement of this system of

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medicine, both philosophical and practical, is found in the Caraka Samhita (the Treatise of Caraka) which has been variously dated from 600 B.C. to 100 A.D., but which is obviously the result of a long series of revisions in the course of its development. 32 At any rate, it was this philosophical physiology which reached the Arabs and was then incorporated into their theories. According to the Indian cosmology there were three major active forces in the great world: water, fire, and air. Essentially these were equivalent to moon, sun, and wind. In addition, earth imparted hardness and Brahman represented the eternal spirit. 33 The corresponding constituents were found in the body of man, where water represented the liquid life energy, fire the essential body heat, and wind in the form of breath the motive force that moved the different parts of the body. The soul, an inseparable part of the living body, corresponded to Brahman. It was infused into the organism at conception and at death rejoined the eternal spirit. Each of the three active physical forces appeared in the form of humors, of which there were three: phlegm, bile, and breath. As was the case with the humors of Greek theory, these had to be in proper balance if the body was to be maintained in health. When such balance existed, each humor carried out its own function. Phlegm lubricated and held the body together. Bile extracted the energy of foods and matured it, and wind, not related to respiration, moved and separated food, produced voluntary and involuntary movement, and conveyed messages from one part of the body to another. 3 4 Food in the stomach was broken up into subtle essence, chyle, which was distributed around the body by ducts of varying sizes. T h e major ducts radiated from the heart, in which was the seat of fire energy. As the essence of the food passed through the liver, it was converted into blood, and this in turn in other parts of the body was converted into flesh, fat, and bone, from the marrow of which the most perfect essence, semen, was formed. 3 5 Waste products remained m the intestine or were carried to the bladder. The ultimate source of body heat was thus the food, and if food was not properly digested, it became a powerful poison. Therefore diet was very important, and the Indian physicians, like their Greek counterparts, were greatly concerned with diete-

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tic problems. As in China, the relation of foods to climate, season and temperament was stressed. 36 Semen, the most perfect essence of the body, was drawn from all parts of the body. Menstrual blood was its counterpart in the female. Semen and blood united at the moment of conception, but no embryo resulted unless the eternal spirit, the representative of Brahman, descended and activated the new embryonic life. T h e fiery energy of blood and the nourishing lunar fluid of semen, the opposite forces which upheld the macrocosm, were united in the microcosm to form the human organism. The individual inherited the firm parts of his body from the father, and the soft parts from the mother. 3 7 T h e uterus acted as a mold to give the fetus its essential shape, though many factors could influence the fetus to produce its individual characteristics. 38 Indian biological theory, though it differs in its details, thus shows the same fundamental philosophical ideas as do the Greek and Chinese theories. T h e macrocosm-microcosm analogy is basic, as is the presence in the body of the vitalizing forces of heat and breath. These are localized not only in specific organs but also in characteristic humors, physical substances, which must be kept in balance for the preservation of health. In view of these basic similarities in all three systems, it is not strange that the Arabs were able to accept and synthesize all the theories which came to them from Greece through the Nestorians of Jundi Shapur and from China and India through the Indian physicians who practiced in Baghdad and translated Indian medical works into Arabic. 39

6 Arabic Concepts

T h e flowering of Arabic culture began with the establishment of the Muslim religion, whose origin is dated from the Hegira, the flight of Mohammed from Mecca to Medina in 622. All Arabic events are dated from this year. In an amazingly short time after this the Arabs had been transformed from a nomadic group of tribesmen in Arabia itself into the rulers of an empire which extended from India in the east to Spain in the west, including almost all of the older Persian, Greek, and Roman territories of Mesopotamia, Egypt, and North Africa. Only Byzantium remained independent and preserved some of the old Greek culture until it fell to the Turks in 1454. Meanwhile the Arabs, after some internecine struggles, established a new capital at Baghdad under the Abbasid Caliphs, whose title means Successor to the Prophet. T h e city was founded in 762 by the Caliph al-Mansur. It was located at the point of closest approach of the Tigris and Euphrates rivers and was not far from Jundi Shapur, the site of the great Nestorian school where theology and medicine were taught. 1 It was natural that when alMansur fell ill and could not be cured by his own physician, he should send to Jundi Shapur for a Nestorian. When the latter

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cured him he began to favor the Nestorian physicians, who were largely of Persian origin. The Caliph al-Ma'mun (ruled 813-829), whose mother was Persian, continued this policy, and Persian influence became strong at court. 2 T h e Arabs soon became aware of the large body of Greek scientific literature which the Nestorians at Edessa and Jundi Shapur had translated into Syriac. They began an active period of translation of this literature from Syriac and even from the original Greek into Arabic. T h e introduction of paper from China when Samarqand was captured in 704 and the establishment of the first Arabic paper factory at Baghdad in 794 made books more easily available. 3 In 828-829, al-Ma'mun set up an institution, the House of Wisdom, for the sole purpose of translating Greek and Syriac manuscripts into Arabic. Under the direction of the famous translator Hunain ibn Ishaq (809-877) most of the important Greek medical books became available to the Arabs. 4 T h e latter were in an ideal position to receive the knowledge of the ancient world. In the golden age of Arabic science, from about 900 to 1100, the court at Baghdad supported scholarship and learning of all kinds. T h e scholars who flourished there drew most heavily on Greek philosophy and science, but they were the heirs even of the Babylonians, and they relied greatly on Persian and other further eastern cultures. Levey has shown that in the materia medica of al-Kindi (801-866) 33% of the names of drugs came from Mesopotamia (usually through other Semitic languages as intermediates), 23 percent from Greek, 18 percent from Persian, 13 percent from Indian, 5 percent from Arabic, and 3 percent from ancient Egyptian. 5 Thus linguistic analysis indicates the central position of the Arabs in drawing together the diverse strands of ancient learning, and this position is clearly evident in their biological theories. However, they were not merely synthesizers of older theories. They impressed upon these theories their own characteristic method of thinking, and from this new insights resulted. Perhaps the most characteristic tendencies of Arabic philosophy were a trend away from abstraction to a more concrete projection for the world around them and a strong desire to classify and arrange facts and theories in a logical order. An example of the first of

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these tendencies is the manner in which they accepted the Aristotelian doctrine of the four qualities. These tended to become actual substances, and the alchemists believed that they could even isolate "cold" as a pure white substance. 6 Similarly the physicians considered the four humors to be actual body fluids. T h e tendency to classify is well seen in the Arabic pharmaceutical recipes. Physicians and pharmacists went far beyond Galen in determining the strength and natures of their drugs. Instead of the simple four degrees of each quality which Galen had used, they introduced finer gradations between these degrees. 7 Haly Abas (d. 994) explained the "secondary faculties" of a drug in terms of its affinity for the organ for which it was intended. 8 Considering every disease, person, and drug as a particular case, alSamarquandi (d. 1222) varied the amounts of a drug he compounded, thus deciding on the exact remedy required. 9 His reasons for this approach were based on a modified theory held by the early Arabic atomists. These thinkers, the Mutakallimun, 10 accepted the atomic theory and believed that each atom possessed in addition to its innate properties a series of "accidents" attached to it. Matter was inseparable from its accidents such as rest, motion, life, death, ignorance, knowledge, combination, separation, cold, and so on. Later philosophers rejected the idea of atoms, but retained the idea of accidents associated with matter. Therefore al-Samarqandi considered not only the humors and their balance to be restored by his drugs but also the accidents attached to these humors. Hence a much broader theoretical approach to the function of the drugs was possible. 11 An excellent illustration of both concretization of an abstract idea and elaborate classification is to be found in the Arabic development of the theory of "the great chain of being." This was a concept which originated in the philosophy of Plato. 12 He envisaged a world in which every possible kind of being must exist in order to fill it up. No genuine potentialities could remain unfilled. Aristotle took up this theory, though he did not believe that everything potential had to exist actually. However, he added from his own philosophy the principle of continuity. He did not believe in atoms and so could visualize a continuous shift of one species into another. His biological observations had convinced

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him that there was often no sharp distinction between animal species. Thus, though he did not arrange animals in a rising order, he did indicate a shading of one species into the next one. The Neoplatonists of Hellenistic times visualized a rising organization of hierarchies up to the supreme spirit, but made this a mystical and religious rather than a scientific concept. Among the early groups concerned with the organization of knowledge in the Arabic world were certain bodies of men who felt the need to compile encyclopedic works based on Greek philosophies. One such group arose among the sect known as the Isma'iliya and produced a vast collection of a very miscellaneous character. This is called the Jabirian Corpus, since they ascribed the authorship to Jabir ibn Hayyan, known as one of the great alchemists of his day. 13 Another group, centered at Basra, was called the "Brethren of Sincerity." 14 Both these groups wrote works deeply affected by Neoplatonic mysticism. They undoubtedly introduced the basic concepts of the Chain of Being which were later developed by individual philosophers. T h e form which the doctrine took in the mind of Abu Ali al-Husain ibn Abdallah ibn Sina (980-1037), called Avicenna in the western world, exerted a powerful influence even to recent times. Avicenna, like many of his contemporaries, clearly differentiated the three kingdoms, animal, vegetable, and mineral. In Avicenna's view, these were connected like the steps of a ladder without any missing link between them. The plant kingdom rested on the mineral, the animal on the plant. T h e highest member of the mineral kingdom resembled the lowest plant, and the highest plant, the lowest animal. Thus the members of each kingdom had all the powers (the Aristotelean "souls") of those below them. Plants had the virtues of minerals plus the vegetative ones, nutrition, reproduction, and growth. Animals had all these plus the faculty of motion, including emotion and sensation. In the highest form of life, man, the rational soul, the intellect, appeared. In accord with Muslim belief, the highest soul was immortal. 15 It can be seen that this highly organized concept of the Great Chain of Being drew on many philosophical sources in its final form. Medicine among the Arabs was strictly divided into the theoretical and practical branches. This was definitely stated in the medi-

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cal work which Hunain ibn Ishaq based on the Mikrotechne of Galen, and which became known as the Isogogue.16 It was with this work that all medical students began their studies. Al-Farabi (d. 950) was well acquainted with this division and knew the philosophy of Aristotle upon which the theoretical part was based. These basic theoretical ideas were derived from the Hippocratic writings and the Aristotelian cosmology, as interpreted by Galen. T h e chief exponent of theoretical medicine was Avicenna. Like many of the so-called Arabic philosophers and physicians, Avicenna was a Persian. He was a versatile genius, interested in all phases of philosophy, and he took Aristotle as his guide, interpreting the latter's doctrines in accord with the Muslim religion and the Arabic character. His greatest importance in the history of medicine was due to his enormous influence on later Arabic authors, and on the Christian writers of the late medieval period. Much of their knowledge of Aristotle and Galen came to them from him, and he was acknowledged as an an authority equal to the older Greeks. He was instrumental in leading Arabic philosophy away from the numerological and Neoplatonic speculations of the Isma'iliya and the Brethren of Sincerity into the more rational lines of Aristotelian thought. 17 T h e chief work of Avicenna in medicine was the Qanun, or Canon of Medicine. The author has been criticized on the ground that he relied too much on earlier texts and reached conclusions only by hypothetical reasoning and speculation, 18 but at any rate, it was this vast compilation of all medical knowledge which became the chief textbook of all physicians until well into the Renaissance period. Like all his contemporaries, Avicenna classified medicine into theoretical and practical parts, and in the first book of the Canon he presented the biochemical concepts which underlay his whole philosophy of medicine. 19 He also summarized his ideas in briefer form in his Poem on Medicine which was also a popular handbook among later physicians. 20 As a good Aristotelian he began with the four causes which govern the human body. The material causes were the breath and members, which are made up of the humors, and these in turn are ultimately composed of the elements. The efficient causes were air, location, and nutrition in the external world, and move-

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ment, excretion, and age in the body itself. The formal causes were constitution, composition, and the faculties, while the final cause was action or function. 2 1 Each of these factors was then considered in detail, with elaborate classifications and subclassifications. T h e interaction of the elements produced the temperaments, of which there were nine, one even, and eight with a predominance of some element. It was the balance of the temperaments which determined the nature and health of the individual. T h e man in whom the temperaments were most evenly balanced was the most perfect. It was generally held by the Muslims that Mohammed had the most even possible mixture of temperaments. 22 When the temperaments were not in balance, one or more of the component elements were dominant and this determined the character of the individual. Aside from the individual differences, however, there were certain general mixtures of temperament which could be recognized. In children and young people warmth dominated, with an increasing amount of dryness as the person matured. The mature man tended to be colder, though males were warmer and drier than females. 23 T h e temperaments expressed themselves physically through the humors, which, of course, showed the characteristic qualities of their constituent elements, though there could be varieties of each. Thus, phlegm was cold and tasteless, but there was a sweeter variety which contained more warmth and dryness, and another which was colder and acid in character. Yellow bile was fundamentally warm, but it could exist in various tints, such as smokey or reddish, as its composition varied slightly. Each humor originated in some particular part of the body. 24 The humors in their turn acted through the members of the body. Of these the chief were the liver, upon which the nutrition of the body depended; the heart, the center of vital heat; and the brain, seat of mental faculties, which kept the heart cool. 25 Finally, the organs functioned through their faculties, which were essentially those of Galen. They were classified as dominant or subservient, the dominant being nutritive, growth, and generative, and the subservient being attractive, retentive, transformative, and expulsive. These faculties pertained to the various organs where their action took place. 26

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On the basis of the components of the body the various processes which occurred in it could be explained. It was generally held that the humors arose from food through a series of coctions. In the stomach the first coction or digestion converted the nutritive portion of the food to chyle, and the residue was partly converted to phlegm, which had no special organ for its formation, or was rejected as waste. T h e chyle passed through the portal vein to the liver, the seat of the natural spirit. There a second coction divided the chyle into three portions: a froth which in the gall bladder became yellow bile, a sediment, which in the spleen became black bile, and the finest portion, which in the liver became blood. T h e aqueous residue was excreted by the kidney because of its expulsive faculty. T h e blood passed to the heart, receiving a third coction on the way, and there combined with spirit from the air to form the vital spirit. A final coction in the brain produced the psychic spirit. There was much discussion of the emotional and psychological factors resulting from the balance of the three spirits. 27 T h e theories of reproduction of Avicenna are again based on Greek sources, but give a more important place to the female than was the case with Aristotle and Galen. T h e male semen was again compared to the clotting agent of milk, and the female "sperm" was compared to the clotted milk. However, it was considered that both substances entered into the substance of the embryo. 28 In his discussion of the practical part of medicine, Avicenna, like other Arabic physicians, stressed the use of drugs. These could affect specific organs by virtue of their content of the various qualities or elements. Seasons, locations, and other factors which also depended on a balance of qualities were also considered. In addition the Arab physician was greatly concerned with the pulse of the patient, possibly influenced · by the Chinese emphasis on this diagnostic aid. He also considered the nature of the excreta, especially the urine, which represented to him the nature of the changes going on in the body. 29 Uroscopy, the visual inspection of the urine, was a standard diagnostic tool, and in more sophisticated form, it still remains a part of a physical examination. Certain remedies recommended by Avicenna are now known to have a rational basis. He advised goose liver for

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treatment of malignant anemia and noted that malaria sometimes helped insanity. 30 T h e Arabs made a further application of humoral theory in considering poisons. They were greatly interested in this subject as were the Indians, from whom they took many of their ideas in this field. Ibn Wahshiya (ninth century) in his book on poisons explained their action because they were substances which "can kill the four simple humors and the four compound ones." 31 He differentiated between a poison, a remedy, and a food. Poison was overpowering in its nature and destroyed the life force of an animal. A remedy reduced a humor which was in excess, though it too might kill "in quantity when it comes together with a certain quality, and when increased, depending on the attributes and condition of the body." A food is such that "the nature of the animal subdues it, ingests, digests, and then transfers it within the body. T h e n it becomes muscle, fat, blood, veins, sinews, and other kinds of matter of the bodies of animals." 32 Almost any reaction observed in the body could be explained in terms of temperaments and humors. This technical knowledge utilized by the medical philosphers and physicians reached into everyday life among the intellectuals of the Arabic world. A number of semipopular medical works appeared under the title Medicine of the Prophet. These purported to be compilations of the sayings of Mohammed on medical topics and consist of short comments on all phases of medicine. It is quite possible that they do incorporate medical ideas from an early period when Arabs had only a simple folk medicine, but in the later form in which they have come down to us they include the theories of humors and temperaments and most of the ideas from Galen and Avicenna, though in simplified form. It is of interest that they state "the Prophet says for every disease God has created a remedy except for old age which is like a disease and ends only in death." 33 An even more revealing example of the diffusion of these doctrines among the populace is the story of the slave girl Tawaddud in the Arabian Nights. 34 This remarkable girl challenged the experts in the fields of theology, music, the exact sciences, geometry, philosophy, medicine, logic, rhetoric, and composition;

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she answered all the questions they could put to her, and then c o n f o u n d e d them by asking questions they could not answer. In the field of medical theory she explained the f o u r elements, the humors, the three spirits, the function of the organs, diagnosis, and the treatment of disease. It is of interest that she declared that the origin of all sickness is corruption of meat in the stomach. This recalls similar theories in Egyptian and Indian medicine. T h u s it is obvious that even in a popular story meant for entertainment the Arab encountered his medical theories, even though in a somewhat simpler f o r m than in his medical classics. In the centuries which followed Avicenna, medical theories did not change in basic character, though naturally some modifications occurred. T h e h u m o r a l theory was less used in the early twelfth century than it had been in the ninth. 3 5 Applications continued to be m a d e as new viewpoints were developed, however. A r o u n d the middle of the thirteenth century ibn Nafis (12ΙΟΙ 288) wrote a commentary on the anatomical section of Avicenna's Canon in which he pointed out that, since the chief function of the heart was the production of vital spirit, the heart should contain both refined blood and air. He held that the blood which came to the heart could not mix directly with air but had first to be refined in a special cavity, the "right cavity." T h e n it had to be transmitted to the "left cavity," where the vital spirit was generated. H e denied the Galenic concept of a direct passage between the two cavities. Hence he believed that the refined blood had first to pass to the lungs to be mixed with air, and, having taken u p the finest part of air, then r e t u r n e d to the heart f o r generation of vital spirit. H e said: " T h a t part [of the blood] which is less refined is used by the lung for its nutrition." From this theory, admittedly m a d e without the possibility of direct anatomical observation, ibn Nafis deduced the lesser circulation of the blood. 3 6 No one in the Arab world acted on this theory, derived f r o m the ideas of Galen and Avicenna but directly contradicting them. It is possible, however, that they may have been known to Servetus or Colombo, who rediscovered the lesser circulation in the sixteenth century. 3 7 A n o t h e r interesting late application of these medical theories in the Arabic world is f o u n d in the work of ibn Khaldun (13321406) in North Africa. H e recounted the old legend that Alexan-

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der the Great was suffocated by being immersed in the sea in a glass coffin. According to ibn Khaldun, death in this case was due to lack of cool outer air reaching the lungs. T h e vital spirit in the heart was therefore not cooled, and Alexander died a burning death. A similar result was to be expected if the outer air was too hot, as in hot baths or deep pits. Fish out of water died because the air was too warm for their normal temperature equilibrium. Ibn Khaldun stressed the importance of maintaining a balance in the body and repeated the Indian idea that illness could result from accumulated residues in the stomach or elsewhere. 38 T h e Arabic medical theories, taken chiefly from the Greeks, but to some extent also from India and China, and impressed with their own character, were thus extremely well organized and consistent and fitted into the world view of Arabic philosophy. When western scholars learned of these theories they too were impressed by the logic of Arabic science and took it over as a basis for the development of their own relatively simple theories. However, from this science they went on to completely new advances which the Arabs never foresaw.

7 The Medieval Period

While Arabic philosophy, science, and medicine were flourishing, western E u r o p e a n physicians had almost no theoretical basis for their medical practice. A few men knew the works of Isadore of Seville, the Timaeus of Plato, and some of the logical works of Aristotle, but these had little impact on the intellectual life of the West. Theology, especially that of Augustine, dominated the thinking of scholars. In the tenth century the situation began to change. Certain local schools began to attract students f r o m outside their own areas. T h e name Studium, generale was applied to some of these. At first they were simply gatherings of students a r o u n d a recognized master, but gradually the relationship grew m o r e formal, rules were established, and charters were issued. T h e first European universities were established. A r o u n d the middle of the tenth century such a school, devoted to medicine, began to function at Salerno. Near the end of the century a more philosophically oriented school arose at Chartres. T h e School of Salerno quickly became the d o m i n a n t institution for training physicians f r o m all over Europe, a position which it held until well into the thirteenth century. 1 In the beginning its

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reputation was based on the practical nature of its teaching, but in the eleventh century more theoretical instruction was introduced. This was in large part due to the fact that the first important translations of Greek and Arabic medical manuscripts began to be collected there. The most important early translational activity was that of Constantinus Africanus (c.1015-1087), who had traveled widely through the Arab countries before settling as a monk at the famous Benedictine Abbey of Monte Cassino, located not very far from Salerno. 2 There Constantinus translated many of the works on medicine which he had collected among the Arabs. These included the writings of Isaac Judaeus (d. 923) on urine, fevers, and diet, and some of the works of Hunain ibn Ishaq, which were themselves translations of Galen and Hippocrates 3 . The most important of these was probably the Isogogue of Johannitus, as it was known in the West. This was a compendium by Hunain based on the works of Galen. It opened with a brief survey of the elements, qualities, humors, energies, and spirits, and the conditions of seasons, winds, and foods which affected the human body. The somewhat simple style of the work is illustrated by the following statements: "Foods are of two kinds. Good food is that which brings about a good humor and bad food is that which brings about an evil humor. And that which produces a good humor is that which generates good blood." 4 Descriptions of diseases follow. Probably because this work briefly epitomized most of the Greco-Arabic medical tradition, it always formed a significant part of the training of medieval physicians. T h e translations of Constantinus became texts at Salerno and spread from there over most of Europe. Thus the influential medical texts of the twelfth century were the more practial books of Hippocrates and Galen, with relatively little stress on the physiological functioning of the human body. Nevertheless, the doctrines of the humors and the four qualities heat, cold, moisture, and dryness were introduced, and these became a standard part of medical thought for hundreds of years. It was, of course, the Arabic elaboration of the original Galen which was taught. In this way the elaborate methods of classification of the Arabs were brought to the west. A clear example of this is found in

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t h e Book of Degrees, in which Constantinus gave a description f o r m e t h o d s of treating specific diseases by diet o r d r u g s . T h e choice of t h e individual f o o d o r d r u g to be used d e p e n d e d u p o n t h e m i x t u r e of qualities which it contained. T h e r e f o r e the d e g r e e of these qualities h a d to be d e f i n e d . For example, a f o o d or medicine was h o t in the first d e g r e e if its heating power was below that of t h e h u m a n body; in t h e second d e g r e e if it was the same as that of t h e body, in the third d e g r e e if somewhat g r e a t e r t h a n that of t h e body, a n d in the f o u r t h d e g r e e if it was e x t r e m e a n d u n b e a r a b l e . Each of these d e g r e e s was in t u r n subdivided into a beginning, a middle, a n d an e n d , m a k i n g an actual total of twelve d e g r e e s of strength f o r each quality. Constantinus laid great emphasis o n h e a t a n d dryness in relation to disease. 2 T h e work of Constantinus was essentially pedagogical a n d preparatory. T h i r t y years a f t e r his death a new series of translations was m a d e at T o l e d o , w h e r e t h e r e was direct contact between Moorish a n d E u r o p e a n scholars. A n u m b e r of translators, such as Domenicus Gundisallinus, J o h a n n e s Hispaniensis, and R a y m u n d of T o l e d o , p r o d u c e d translations not only of lesser works b u t also of the m a j o r philosophical a n d scientific writings of Aristotle, especially as c o m m e n t e d u p o n by Avicenna a n d Averroes. In t h e latter p a r t of the twelfth century a third a n d final set of translations was m a d e in Spain, carried o u t by G e r a r d of C r e m o n a (1114-1187) a n d his colleagues. At this time t h e details of Greco-Arabic science were filled in. In medicine this included the r e m a i n i n g available works of Galen a n d of most of the i m p o r t a n t Arabian physicians. Now everything n e e d e d f o r a complete system of medicine was at h a n d , a n d t h e system which resulted d o m i n a t e d medical t h o u g h t t h r o u g h t h e fifteenth century. 5 T h e i n t r o d u c t i o n of t h e philosophical a n d scientific works of Aristotle h a d a p r o f o u n d e f f e c t o n all phases of western intellectual life. At C h a r t r e s t h e Aristotelian doctrine of m a t t e r a n d f o r m was first discussed a n d t h e n disseminated to t h e learned world. 6 T h e doctrine of t h e elements was applied to living beings t h e r e by William of Conches (d. c. 1159), who classified animals in these terms. Animals consisted chiefly of water, b u t d i f f e r e d f r o m each o t h e r in terms of t h e a d m i x t u r e of o t h e r elements. Birds contained m o r e air, choleric animals like the lion had m o r e

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fire, phlegmatic ones like pigs m o r e water, and melancholic ones like the ass or cow had more earth. T h e h u m a n body had an unusual h a r m o n y of all f o u r elements. 7 For a time there was considerable discussion a m o n g theologians and philosophers as to which of the two leading interpretations of Aristotle by Arabic commentators should be accepted. Even a m o n g the Arabs there had been conflict between the followers of Avicenna and those of Averroes, a more materialistic philosopher. This conflict continued in the west, but ultimately the views of Avicenna prevailed, largely because they were m o r e compatible with Christian doctrine. Avicenna believed in personal immortality, a view Averroes had denied. After the midthirteenth century the influential teachings of the greatest intellectual figures of the day, Albertus Magnus (1206-1280) and T h o m a s Aquinas (1224-1274) became d o m i n a n t at the University of Paris, the scholarly center of E u r o p e at this time. They were strong Aristotelians, and so the teachings of Aristotle became the foundation of philosophy in all fields, including medicine. His ideas f o r m e d the basis of every discussion. 8 T h r o u g h o u t the thirteenth and fourteenth centuries all medicine was taught on the foundation of the Greco-Arabic medical principles. New medical schools at Bologna, Montpellier, and Paris replaced Salerno as chief center of medical education in the thirteenth century, and at these the translations of the T o l e d o school f o r m e d the standard textbooks. At Montpellier the chief authorities were Galen, Avicenna, Rhazes, and the translations of Constantinus. 9 At Paris, which served as the model for most of the m a j o r E u r o p e a n universities, the students read Aristotle's De animalibus and Meteorologica in additon to their medical texts. 10 T h e physicians trained in these schools naturally tended to devote themselves to their professional duties of caring for illness. W h e n they wrote books of their own, these were usually descriptions of the various diseases they encountered and the treatments they used. T h e r e was an increasing tendency to include what they called experiences or experiments, but these were hardly what a m o d e r n scientist would call experiments. Rather they r e p o r t e d modifications of the usual methods of treatment or of the usual drugs. Much space in the medical literature was taken u p with descriptions of the drugs, usually classified in terms of their con-

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tent of the various qualities. Beyond this, not much theory was f o u n d in these medical works. T h e doctrines of the qualities and h u m o r s were too well standardized and accepted to require much attention. A few examples will indicate how casually medical theory was treated. Gilbertus Anglicus, writing betwen 1230 and 1240, began his discussion of fevers by quoting the appropriate definition f r o m the Isogogue, "Fever is an unnatural heat, that is, heat which overpasses the normal course of nature and it proceeds f r o m the heart into the arteries and is h a r m f u l by its own effects." H e then goes on to describe the different types of fevers clinically. 11 Petrus Hispanus (d. 1277) asked a series of questions, many of which are concerned with medical and dietary problems and answered a n u m b e r of them in terms of the balance of the f o u r qualities. T h u s , dove's blood removes spots f r o m the eye because of its heat and moisture. Sparrows, epileptic themselves, cure epilepsy because they are very hot and dry and so can consume the h u m o r s and vapors which cause epilepsy. 12 A similar series of concerns was examined by Peter of Abano (1250-c. 1316). These included such questions as "Is vital virtue something different f r o m natural and animal virtue?", "Is every cure by contrary?", or "Is the white of an egg hot, but the yolk cold?" 13 T h e last question was inspired by the Aristotelian belief that a chicken develops f r o m the white of an egg and uses the yolk for food. 1 4 T h e surgeon H e n r y de Mondeville (1260-1320) believed strongly in the power of n a t u r e to cure disease. In explaining the course of development of an abscess left untreated he described how at first the material of the abscess caused swelling. H e r e n a t u r e did not act on the material. As growth continued, n a t u r e began to act on the abscess material, but not sufficiently against it. At the height of the condition, growth stopped and the natural virtue, or power of nature, became dominant over the material of the abscess. T h e abscess subsided a n d disappeared or was transf e r r e d to a n o t h e r site. W h e n a foreign substance was expelled f r o m the body, it was because the substance liberated a rottenness, and nature acted a an expelling force. 1 5 T h e s e examples show that the theories of Galen and Hippocrates, expressed in Aristotelian terms, were used so routinely that physicians seldom f o u n d it necessary to mention them explicitly.

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However, some m e n were beginning to modify these theories in the light of their own experience and to introduce new interpretations while still retaining the skeleton of classical ideas. This is clearly shown in the theoretical portion of the Chirurgia magna of Guy de Chauliac (c. 1300-1368), which was one of the chief surgical texts of the later Middle Ages. Written in 1363, it circulated in manuscript and was first printed in France in 1478. It remained influential t h r o u g h the sixteenth century. 1 6 Guy accepted the idea of the f o u r humors, but classified them in the new way into two groups: natural and unnatural. T h e natural h u m o r s arise f r o m ingested food which is separated f r o m extraneous matter and converted to liquid chyle in the stomach and intestines. This is then carried to the liver, where it is transf o r m e d by heat into the natural humors. T h e s e are the "matter of n u t r i m e n t " and are carried by "containing blood" to all parts of the body to be converted to body substance. T h e r e is some confusion h e r e between blood as one of the h u m o r s and "containing blood" which transports them. T h u s there is true and p u r e blood, choleric blood, phlegmatic blood, and melancholic blood. However, according to Guy, only the containing blood can nourish the body, since it alone is the blood which contains all f o u r humors. Guy f u r t h e r subdivided these natural humors, and the u n n a t u r a l ones into unnatural-useful and unnatural-noxious humors. T h e useful h u m o r s have specific functions for individual organs. T h e melancholic h u m o r stimulates appetite in the stomach, the choleric stimulates defecation in the intestine, the phlegmatic lubricates the joints. Blood carries the unnaturalnoxious h u m o r s toward the periphery of the body for expulsion. T h o s e not expelled cause fevers, and those reaching only the surface of the body cause skin diseases. In a m a n n e r rather inconsistent with the above classification, Guy also divides the h u m o r s into normal and abnormal. H e r e he comes back to the theory of qualities of Galen and Avicenna, which played little part in his other speculations. T h e physical properties of the humors, such as color or taste, derive f r o m the complexion, or proportion of each quality (hot-moist, and so on) in the h u m o r . Abnormal h u m o r s are those whose complexion

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varies too much from the norm of the normal humors. It is clear that Guy is torn between an attempt to adhere to the older theories by which to explain physical properties and newer and more original attempt to explain physiological function in terms of specific substances, a truly biochemical approach. He shows the uncertainty typical of a transitional period in intellectual history. The need for new interpretations of classical theory became more apparent at about the same time because of the new situation caused by the introduction of the Black Death which appeared in Italy in 1348. T h e traditional Galenic view of plague was that it originated either from air corrupted by dead bodies, from stagnant water, or from harmful humors caused by something in the diet. Rhazes in the ninth century had suggested that decaying blood produced an effervescence in the body, but this rather chemical idea had not been taken up. Many physicians simply blamed the disease on the astrological position of the stars. T h e rapid spread and extreme severity of the Black Death now led some men to think more carefully about the possible causes. 17 Gentile da Foligno (d.1348, probably of the plague) combined the older doctrines into a specific mechanism. He admitted that the remote and initial cause of the plague was the disposition of the stars, but he believed that this acted through a corruption of the air which engendered poisonous matter around the heart and lungs. T h e disease could not be explained merely by an excess in the degree of some of the primary qualities, as was the case for most illnesses, but came from the property of the poison vapors and air which was breathed. This accounted for the contagious nature of the plagaue. For treatment he used drugs whose value did not derive from the mixture of elementary qualities (number of degrees of each quality) but came directly from the stars. He asked how air could be corrupted when it is a simple element and corruption is a function of mixed bodies. T h e reason was that air does not putrefy in its own sphere or simple state, but does so when mixed with terrestrial or watery vapors. 18 Marsilio Ficino (1433-1499) believed that the plague did indeed arise from a poisonous vapor in the air, but this vapor did not act directly on the humors as Galen had held. It was poisonous because of a specific action like that of arsenic. This affected the

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vital spirit of the heart directly, producing an effervescence, first of the spirit, then of the humors. This theory of a specific chemical action foreshadowed the later theories of the iatrochemists. 19 T h u s , even in the f o u r t e e n t h century the theories of Galen were being challenged a n d the idea of specific action by specific substances was appearing. A still clearer view of the place of Galenical and Aristotelian ideas in the thinking of educated medieval m e n can be obtained by noting how these ideas were borrowed by laymen and used to account for known p h e n o m e n a . T h e s e they attributed to the behavior of the substances which constitute the h u m a n body and the m a n n e r of their interactions. O n e of the earliest medieval writers to utilize the Greco-Arabic biological theories was a remarkable woman, Hildegard of Bingen (1098-1179), abbess of a convent on the Rupertsberg near Bingen on the Rhine. 2 0 She combined the qualities of a mystic who saw and recorded ecstatic visions with those of a very practical woman of affairs who managed her sisterhood, treated illnesses, and corresponded extensively with emperors and popes. She was greatly interested in the science of her day, and she had access to the library of a nearby bishop which contained the medical works of Constantinus and the school of Salerno. It is known that she studied these, since at one point in h e r works she uses the Arabic term sifac, which was used by Constantinus f o r the peritoneum. 2 1 She did not know the works of Aristotle, since the Toledo translations had not reached Germany between the years 1150 and 1157, which as she states, she spent in the study of nature. 2 2 She was a strong believer in the macrocosm-microcosm theory and introduced it not only into her scientific writings but also into her theological and visionary ones. 2 3 T h e organs of the body corresponded to various heavenly bodies and meteorological p h e n o m e n a . T h u s , when the heart is stirred by emotions, h u m o r s are excited in the lungs and these rise to the brain and are emitted t h r o u g h the eyes as tears. I n the macrocosm the equivalent is the waxing or waning of the m o o n which arouses the winds. T h e s e raise fogs f r o m the seas and other waters. 24 Hildegard also described in detail the physical and emotional characteristics of the choleric, sanguine, melancholy, and phlegmatic man.

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H i l d e g a r d wrote two scientific books. In the Physica she described animals a n d plants as well as minerals, a n d discussed t h e m in terms of the elements a n d qualities. In Causa et Curae she treated of medical ideas a n d devoted m u c h attention to individual f o o d s a n d t h e conditions u n d e r which they should be used. It was h e r e that h e r biochemical views were most clearly expressed. H e r theories of digestion, basically Galenic, contained some ideas which were probably original with her, as in the following extract. W h e n o n e eats, the little veins which perceive taste distribute this t h r o u g h the body. T h e finer juice f r o m the food is taken by t h e i n n e r veins, thus those f r o m the liver, t h e heart, a n d the lungs, f r o m the stomach a n d these carry it t h r o u g h t h e whole body. In this way the blood increases in m a n a n d the body is n o u r i s h e d as fire by the bellows is b r o u g h t to b u r n i n g , and grass g r e e n s a n d grows by wind a n d dew. T h e n as the bellows increase the fire a n d wind a n d dew b r i n g grass, so the juice f r o m food a n d d r i n k originates blood a n d s e r u m a n d also flesh of m e n a n d increases t h e m . But as t h e bellows is not fire, a n d wind a n d dew are not grass, so n e i t h e r is t h e juice f r o m food blood n o r juice f r o m d r i n k s e r u m , but t h e j u i c e f r o m food is colored like blood a n d t u r n s into this, a n d t h e juice f r o m d r i n k takes t h e color of s e r u m a n d remains in this. Both so build the blood to a liquid a n d allow it to rise as leaven does the whole mass of flour; that is t h e d o u g h , a n d this remains in it, unites in this way with it a n d in it a n d becomes used u p . W h a t e v e r is left over f r o m the used food a n d d r i n k sinks to t h e lower p a r t of m a n , changes to p u t r i d m a t t e r a n d w h e n it has become p u t r i d is s e p a r a t e d off f r o m m a n as w h e n g r a p e s a r e u s e d in t h e wine press, the wine is d r a w n off in a vessel, a n d what is left over, that is, the peelings, a r e t h r o w n out. O n n u t r i m e n t . If m a n eats a n d drinks, the trait characteristic of life which lies in m a n a p p e a r s , t h e taste, the finer juice a n d o d o r of f o o d a n d d r i n k a r e carried u p to the brain a n d w a r m this so that all t h e little veins a r e filled. T h e o t h e r p o r t i o n of f o o d a n d d r i n k which goes to t h e stomach warms the heart, liver, a n d lungs. T h e s e d r a w f r o m t h e same taste the finer j u i c e a n d o d o r to t h e veins so that these a r e filled, w a r m e d , a n d n o u r i s h e d as w h e n a whole d r i e d piece of gut lies in water it softens a n d swells a n d fills. So will it be if a m a n eats a n d drinks; his veins are filled

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and warmed by the juice from food and drink so that this juice warms the blood and serum in the veins and the blood which is in the flesh draws its red color from the content of the veins. 25 Although Hildegard did not know Aristotle, the efforts of the Toledo translators soon made his works available, and in the thirteenth century he became widely known. Both his scientific and his philosophical works were hotly debated. The ultimate triumph of the Avicennans over the Averroists was largely due to the views of the two great theologians of the century, who expounded the opinions of Avicenna: Albertus Magnus and Thomas Aquinas. Albertus Magnus was most interested in the scientific treatises and in physiological mechanisms. T h e Greek idea of the various souls had been modified by both the Arab and the Christian philosphers to bring it more into accord with their theological concepts. Although the metabolic aspects of the various soul were no longer so heavily stressed, they were not completely abandoned. T h e rational soul, unique to man, had become the immortal soul of theology, but it still controlled the body. Albertus Magnus felt that something was required to mediate between this soul and the body. This mediator, the spiritus, he placed in the heart. It is obvious that this is the vital spirit of earlier thinkers. His idea was graphically shown in a series of thirteenth century anatomical drawings which showed a black grain in the heart, from which the arteries arose. This probably indicated the point at which the spiritus entered the arteries and was distributed to the body. 26 A considerable part of the extensive writings of Albertus comes directly from Aristotle, but in his descriptions of animals and plants he included a number of his own observations and interpretations. This is illustrated by his embryological theories. He made original observations on the developing eggs of hens and fishes. He departed somewhat from Aristotle by accepting the Epicurean view that in the process of conception both male and female supplied a seed. In the development of the embryo the male seed coagulated the female seed, and then the menstrual blood supplied the material to form the new tissues. Since he accepted the Aristotelian idea that bird emryos come from the

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white of the egg, he compared the menstrual blood to the yolk as a source of material. Each part of the animal—bones, flesh, fat—came from a certain part of the blood, activated by the sperm. He said: "Other parts of the blood are its refuse and impurities, and are not attracted to the generation of any part of the animal, but having been collected until birth, are expelled with the embryo from the uterus in the fetal membranes, like the remnants in the hen's egg after the chick has hatched. There is a similar virtue in the liver and heart of animals, which organs after the animals are born form the flesh and fat from food in accordance with its twofold substance and expel the refuse as we said before." 27 Even more influential in establishing the dominant philosophy was the thoroughgoing acceptance of Aristotle by Thomas Aquinas, the favorite pupil of Albertus Magnus. While he was less interested in science than was his master, he encountered a number of scientific problems in his theological writings, and his explanation of these was always Aristotelian. Aquinas had moved away from the Greek idea of the various souls which animated the living body and governed its metabolic functions. He believed that the nutritive and other lower souls operated in the lower life forms, but in man only the rational soul was present. Thus the Christian view of body and soul could be reconciled with Greek philosophy. Aquinas believed that the rational soul is the form which actualizes the potentiality of matter which is the body. He thought that the developing fetus first received the vegetative soul, which ultimately died and was replaced by the sensitive soul. This in turn was replaced by the rational soul, directly provided by God. and this soul continued to function throughout life. 28 On these largely theological grounds he rejected the idea that the soul needs a medium to control the body, and so differed from Albertus. 29 The idea of soul and body, form and matter, appeared in his attempt to explain the difficult problem of what occurred when one body was eaten by another. In lower animals this was not so difficult to explain. When a goat was eaten by a lion, the goat flesh simply received the form of the lion. 30 However, when a human was eaten by a cannibal, the problem was more complex,

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since on the day of resurrection it was a question of whose body would rise again. In his Summa contra Gentiles, Aquinas solved this with considerable insight. 3 1 H e pointed out that, t h o u g h m a n remains m a n t h r o u g h o u t his life, the parts of his body are continually f o r m i n g and breaking down. This he compares to a fire which continues to b u r n and is thus the same fire, but has to be supplied with fresh logs to keep it burning. H e said: "It is the same with the h u m a n body, since each part retains its f o r m and species d u r i n g the whole of the lifetime whereas their matter is both dissolved by the action of natural heat and renewed by means of nourishment." T h e r e are echoes of Heraklitos here. O n this basis Aquinas concludes that the flesh of the victim which was first perfected by the rational soul will rise again, while the cannibal will be resurrected only with the matter he received f r o m other food. An even m o r e clearly Aristotelian, a r g u m e n t appears in a letter which Aquinas wrote to a certain Master Philip, probably between 1270 and 1273. In this he attempted to explain the motion of the heart. 3 2 T h e problem was to determine what moves it, since Aristotle says everything that is moved has a mover. In true scholastic fashion, Aquinas considered a n u m b e r of possible causes, presenting the arguments on both sides and finally reaching his own conclusion. It had been said that the vegetative soul could not be the mover, since plants have this soul, but no heart. T h e sensitive soul had been rejected, since this is moved by desire, and heart motion is involuntary. It was also said that the motion could not be natural, since natural motion is in one directon only, as u p w a r d f o r fire and downward for earth, while the heart has a push-pull motion. H e a t generated t h r o u g h a spirit cannot be the cause, f o r a cause is prior to an effect, but heat is an effect of motion. Aquinas then quotes extensively f r o m the biological books of Aristotle to conclude that the motion is natural, since it is essential to animal life. T h e r e f o r e it must be produced by the highest soul, the sensitive soul in animals and the only soul in man, the rational. It t h e n remains to explain how the motion can be natural. This is because it approaches perfect motion, which is circular, but falls a little short of it. Circular motion r e t u r n s to the same point f r o m which it started, and the push-pull motion does the same. Finally, Aquinas points out that emotions

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of the soul can cause changes in heart function. Thus by a combination of the physics and biology of Aristotle he has proved that the heart is moved by the soul, and its motion is natural. Another thirtheenth-century scholar, a man of marked originality and the source of many controversies, was the Franciscan friar Roger Bacon (c. 1212-C.1292). He has been especially noted for his stress on the value of "experimental science," which he classed as a separate subject in its own right. While he accepted much of the astrology and superstition of his day, he put more emphasis on the need for a more scientific approach to the problems of the day then did many of his contemporaries. He even explained the marvelous in terms of his science rather than magic. Thus, in the case of the woman of Norwich who ate nothing for twenty years, yet was in perfect health for all that time, he concluded that some constellation must have reduced the concourse of the four elements in her body to a self-sufficient harmony seldom attained on this earth. However, .only the resurrected body could have a perfect balance of elements and so remain for eternity. 33 Bacon expressed his confidence in the experimental method very strongly in a critical manuscript which he probably wrote between 1268 and 1278, the "Errors of the Physicians." 34 In this he criticized the medical profession for its ignorance of the true causes of the diseases which it treated. T h e four humors might be involved in disease, but no one knew how they operated or why their excess or deficiency should cause disease. He admitted that it was more difficult to experiment on the living body than on an inanimate object, but experiment remained the only proper approach. He placed the greatest reliance on what he called alchemy, which was actually allied to the modern concept of chemistry. Alchemy would some day disclose the stuff out of which man and the universe were made. It could already be used to separate the various humors from the blood and in the future might show how they carried out their appointed tasks. As in many other cases, Bacon foresaw the possibilities of science far more clearly than did most of his fellows. A less learned explanation of body functions, but one that probably reached a greater greater number of people than did the works discussed above was the Buch der Natur, the first book on

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natural science in German. It was composed by Konrad von Megenberg (1309-1374) about 1350. Konrad studied theology and philosophy at Paris, and in the first part of his life was active in politics. After a severe illness, he entered the church and spent his last years at Regensburg. It was his desire to bring to his countrymen the knowledge of nature which was contained in numerous Latin works of the day, and so he compliled the Buch der Natur, which became extremely popular. In its discussion of soul, spirits, and body it probably influenced the later theories of Paracelsus. 35 It is significant for the picture it gives of the ideas of an educated fourteenth-century man on the structure of the world and the workings of the human body. 36 Naturally, everything is based on the theory of the four elements and the qualities. Plants and animals are discussed in some detail, and much attention is paid to the physiology of nutrition. According to Konrad, food is first acted upon in the stomach, where it forms a clear liquid like barley water. "Through the power of Nature" this is separated from the undigested residues, which are excreted. T h e digestive process in the stomach lasts for some time, since the lining of the stomach is made up of folds which retain the food. If the lining were smooth, the food would quickly slip out undigested. After digestion, the nutritive portion passes to the liver, where further action takes place. This action is aided by the presence of bile, which is hot, dry, and fiery. Therefore it can heat and dry out fluids as fire does and thus helps to work up the nutritive material from the stomach. In the liver there is a further separation of water, which is carried to the kidneys and bladder, while the true nourishment is changed into blood and carried to the other organs. Each organ further works u p the blood it receives according to its own ability, until everthing is completely assimilated. T h e most important organ is the heart, where the blood is changed to natural heat and vital spirit. In accord with theological doctrine Konrad makes it clear that this spirit is not the soul, since the soul is the substantial being whose action gives life to everything which it permeates. It can be seen that this somewhat simplified explanation of digestion and nutrition is basically that of Galen as transmitted by the Arabs and given a theological twist by medieval philosophy.

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While it is evident f r o m the foregoing that the ideas of Galen and Aristotle dominated the thinking of almost everyone in the thirteenth century, a change was at hand. In the fourteenth century a more skeptical attitude a p p e a r e d a m o n g the philosophers, the scientists, and even some of the physicians who still adhered to the theories of Galen. William of Occam (c. 1300-1350) introduced a logical approach to philosophy which led to a more scientific and mathematical idea of nature. T h e O x f o r d school of physics challenged Aristotle's views on motion, and their work finally led to the physics of Galileo. 37 T h e challenge of the physicists soon began to affect even those concerned with biological problems. Such a physician was Arnald of Villanova (d. 1311) who fully accepted the humoral pathology of Galen and the astrological theories linking the planets with the f o u r qualities and the organs of the body, yet believed that the world had grown old and d i f f e r e n t compared to what it was in the days of Galen. T h e r e f o r e the experiences of the ancients had to be adapted to m o d e r n times. A wise physician with the increased knowledge available to him could overrule the effects of the stars because of his superior reason. H e could recognize their evil dispositions and improve them by an appropriate remedy. 38 Perhaps even m o r e influential in bringing about a change in the theories of structure and function of the h u m a n body were the new discoveries of the alchemists and technologists of the thirteenth and fourteenth centuries. T h e great improvement in the art of distillation was a m o n g the most important of these. From the early Mesopotamian days relatively c r u d e distillations had been carried on, but the lack of efficient cooling devices had prevented the recovery of anything but the highest boiling substances in the distillate. Now a major advance was m a d e in the condenser, and as a result new substances such as the mineral acids and alcohol were obtained. 3 9 Most of the alchemical writings of the thirteenth century mention alcohol u n d e r the n a m e of aqua ardens or a similar synonym. T h e full medical implications of highly purified alcohol were first emphasized by J o h n of Rupescissa, who flourished in the mid-fourteenth century. 4 0 In his work "On the consideration of the fifth essence" he e x p o u n d e d the w o n d e r f u l properties of alcohol in preserving the body f r o m corruption. It

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could not make man immortal, but it did not act like the ordinary four elements, each of which could confer only two of the qualities on a body. Alcohol could confer any quality' needed at the moment, and was analogous to Aristotle's fifth element, the quintessence, of which the heavenly bodies were composed. 41 John then proceeded to generalize this concept. Since the quintessence was obtained from wine, it must have been present in the wine to begin with. In the same way, all other substances must contain a quintessence which was also to be obtained by distillation. Herbs and animal matter could yield a quintessence, but he was more interested in metals such as gold, antimony, and mercury. By chemical treatment these metals could be reduced to solution and the solutions distilled to give the desired product which would have the wonderful powers of all quintessences. Multhauf believes that this discovery and the implications drawn from it furnished the basis for medical chemistry which ultimately overthrew the system of Galen. 42 The idea of the extraction of quintessences by distillation and using them to cure bodily ills shifted the emphasis of alchemy from the idea of making gold to that of extracting active principles. True, the idea of gold-making continued to influence many alchemists, but some of them began to regard their science somewhat as the old Chinese alchemists had done, as a source of medicines. In 1500 Hieronymus Brunschwygk published his Liber de arte distillandi de simplicibus in which he described the distillation of plant materials to produce substances which would "make the body more spiritual, the unlovely lovely, to make the spiritual lighter by its subtility, to penetrate with its virtues and the force concealed in it into the human body to do its healing duty." 43 Another factor leading to the introduction of experimental methods into chemistry and biology was the growing tendency to use the balance in technological work. T h e metallurgists of the period certainly weighed the samples they assayed, and several physicists, including Jordanus Nemorarius in the thirteenth century and Blasius of Parma (d. 1416), had written on the balance. 44 One of the most outspoken advocates of the value of weighing was the busy theologian and man of affairs, Cardinal Nicolaus

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of Cusa (1401-1464). 4 5 H e was a m a n of wide-ranging interests who foresaw some of t h e f e a t u r e s of the C o p e r n i c a n system a h u n d r e d years b e f o r e C o p e r n i c u s a n d went beyond the latter in his speculation of the infinite universe. H e wrote o n astronomy and mathematics as well as o n c h u r c h politics a n d theology. A b o u t 1450 h e published a book called The Idiot, a series of dialogues between a n "idiot" a n d an "orator" in which t h e idiot by his c o m m o n sense a n d advanced outlook enlightened a n d amazed the orator. I n the f o u r t h book of this work, De staticis experimentis, the idiot explained what could be learned by the use of t h e balance. H e h a d a clear idea of specific gravity a n d of possible medical a n d chemical o p e r a t i o n s involving weighing. H e suggested that by weighing equal volumes of the blood or u r i n e of "a healthy m a n a n d a weak one, of a y o u n g m a n a n d a n old, of a G e r m a n a n d a n A f r i c a n " variations in t h e fluids could be detected a n d diagnosis of d i f f e r e n t diseases could be m a d e . T h e choice of h e r b s to be used in t r e a t m e n t could also be thus determ i n e d . T h e pulse might be c o u n t e d by weighing the a m o u n t of water which fell f r o m a water clock while t h e pulse of a healthy m a n gave a h u n d r e d beats, a n d this s t a n d a r d could be c o m p a r e d to the pulse beat of an individual with some disease while t h e same a m o u n t of water flowed out. Rates of respiration could b e d e t e r m i n e d in a similar way. T h e a m o u n t of water in a plant could b e f o u n d by weighing it, ashing, a n d d e t e r m i n i n g t h e weight of the ashes. A p p a r e n t l y these ideas were suggested simply as possibilities a n d Nicolaus did not carry t h e m out, b u t they show that t h e idea of quantification h a d b e g u n to reach biological thinkers as well as physicists at this time. T h e actual p e r f o r m a n c e of such e x p e r i m e n t s b e g a n in t h e next century w h e n V a n H e l m o n t carried o u t his willow tree e x p e r i m e n t a n d Sanctorius d e t e r m i n e d t h e a m o u n t of "insensible p e r s p i r a t i o n " given off by m a n . T h e s e workers did not acknowledge the priority of Nicolaus, possibly becaue his theological activities h a d m a d e him u n p o p u l a r a m o n g both Catholics a n d Protestants. 4 6 It can b e seen that t h e biochemical concepts of t h e medieval period were not fixed, t h o u g h they did n o t c h a n g e rapidly over the course of 400 h u n d r e d years. B e g i n n i n g with t h e introduction of Greco-Arabic philosophy a n d medicine t h e r e was a period of

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full acceptance of these, followed by their gradual modification. Philosophy, medicine, and alchemy all passed through these changes, and each influenced the others as the changes occurred. Throughout, however, the doctrines of the four elements, the four qualities, the four humors, and their balance or imbalance dominated the minds of all thinkers. Yet the materials for a new synthesis were slowly appearing. In the sixteenth century one man took these materials and drastically rearranged them by his own concepts. With Paracelsus the modern science of biochemistry may be considered to have begun.

8 Paracelsus and the Beginnings of latrochemistry

Theophrastus Bombast von Hohenheim (1493-1541), better known by the name he assumed later in life, Paracelsus, marks the decisive turning point away from the generalized doctrines of Aristotle and Galen to the more specific approach which became characteristic of medicine, physiology, and chemistry during and after the sixteenth century. T h e general outlines of his life and thought are well known, though there are many missing details and many contradictions in the accounts of each. 1 His father was a physician. He was brought up in a mining region, and from his early life was familiar with metallurgy and the technical chemistry of his day. Among the writers who influenced him was Abbot Trithemius of Sponheim, a celebrated alchemist. He studied medicine in various European universities, though it is not certain that he ever took the degree of doctor of medicine. He was of a remarkably restless and quarrelsome disposition. His life was spent in wandering from city to city, and he remained in each only long enough to antagonize almost all the influential citizens and induce them to expel him from their

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city. At the same time he was absorbed in observations of n a t u r e and in developing his own very characteristic philosophy. All these influences a p p e a r in the system he worked out and advocated violently. H e was at once a mystic, a philosopher, an experimental chemist, an innovating physician, and a rebel against all authority. It is no wonder that such a contradictory character produced a body of work which is itself full of contradictions. T h r o u g h o u t his life his ideas developed and changed, and this is reflected in his various books. He was addicted to the invention of strange names for the forces and substances he described, and he often altered the definition he had given earlier f o r these. Such changes confused and irritated even his own followers. H e wrote in colloquial G e r m a n rather t h a n the customary learned Latin, and his language was abusive and violent toward all who opposed him. Naturally there were many who did, especially a m o n g the physicians a n d scholars whom he irtsulted. His lifelong antipathy toward the theories of Galen and Avicenna reached its climax in the celebrated bonfire of J u n e 24, 1527, when he b u r n e d the Canon of Avicenna in the public square of Basel. This was part of his attack on the orthodox physicians of the day who had been trained in the works of Galen and Avicenna. H e insisted that his own system of medical theory and his pharmaceutical preparations had r e n d e r e d their training of no value. H e claimed a very large n u m b e r of cures in cases in which the Galenic remedies had failed. Some thought him a magician, some a quack. Although most of his medical works were not published until after his death, he attracted many faithful followers while alive, and these m e n saw to it that his theories eventually reached the public. His influence spread m o r e and m o r e widely d u r i n g the sixteenth and seventeenth centuries. A consideration of his system of medicine show the decisive t u r n which he gave to physiological theory, a t u r n which ultimately led to a biochemical approach to the functions of life. T h e sources of Paracelsus' theories lie d e e p in the philosophy of western man. 2 Pagel has traced these in detail and shown that the basic ideas of medieval scholars were present in the mind of

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Paracelsus even when a direct connection cannot be shown. T h e remarkable feature of the Paracelsus system is not that its materials were completely novel but that he was able to synthesize these materials into a system that altered the whole approach to the human body. His method of attack was not rational but rather intuitive and interpretive of nature. 3 He loved analogies and used them constantly. T h e fundamental idea which underlay the entire system of Paracelsus was the correspondence of macrocosm and microcosm. Every organ in the body "corresponded" to an astral body which could exert an effect on it. T h e heart was the microcosmal sun which distributed warmth and fluid for maintenance of nutrition and the growth of the other organs, each of which had its own heavenly counterpart. 4 This did not mean that the astral body had an effect on the living organism, though the distinction between causation and correspondence was not always clear in Paracelsus' writing^ T h e living body was the key to an understanding both of man and of the cosmos. T h e view of Paracelsus was essentially dynamic and he had little use for dissection of the cadaver. He said, "You will learn nothing from the anatomy of the dead; it fails to show the true nature, its working, its essence, quality, being and power. All that is essential to know is dead. T h e true anatomy has never been dealt with. It is that of the living body, not of the dead one. If you want to anatomize health and disease, you need a living body." 5 Paracelsus used the term anatomy in various ways but not in the sense that is current today. He believed in chemical anatomy, examination of the various parts of the body to discover the affinity in the composition of the individual parts with the individual substances in the outside world, the parallelism between the macrocosm and the microcosm, and correspondence of the bodily parts with the stars. 6 The functioning of the body, then, had to reflect the manner in which the world came into being and continued to exist. It was Paracelsus' firm belief in alchemy and his knowledge of technical chemistry which formed the basis of his cosmology and biology, for these were one and the same to him. T h e basis of practical alchemy as it had developed over the previous centuries

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was the separation of material substances f r o m a prime matter, and then the separation of the p u r e substances f r o m the impure. These processes could be carried out only by chemical methods, and such methods he set himself to discover. T o Paracelsus the chief weakness of Aristotle was that he was ignorant of chemistry and alchemy. 7 H e held that all things are created f r o m a prime matter, the mysterium magnum, itself uncreated and eternal. T h r o u g h separation and condensation the f o u r elements appeared. T h e s e did not have the "complexions" of the Aristotelian elements, that is, they were not mixtures of two qualities. Fire was not m a d e u p of hot and dry, it was simply hot. T h e elements were not fixed, they were the dynamic matrices out of which objects arise; they were the soil f r o m which objects a p p e a r e d as their "fruits," and they continued to maintain these objects. All the objects arising f r o m a single element were related. For example, m a n comes f r o m earth and shares with other plants, minerals, or spiritual emanations which come f r o m earth the virtues of earth. 8 However, these objects do not arise directly. T h e three principles are the first products coming f r o m the elements, and varying mixtures of them make u p the ultimate objects. T h e s e principles are the famous tria prima of Paracelsus, mercury, sulfur, and salt, representing the properties of vaporosness, combustibility, and solidity. T h e Arabian alchemists had developed the theory that metals consist of mercury a n d sulfer; Paracelsus extended this concept to all substances and a d d e d salt as an essential constituent. 9 In the essentially dynamic theory of Paracelsus, something was needed to carry out the construction of the elements, the principles, and the objects which they compose. Paracelsus personalized the forces which he required. T h e reservoir of material f r o m which objects are m a d e he called the Iliaster (hyle-aster, star matter). T h e workman who perfected this prime material to ultimate matter was the Vulcan. In o r d e r to assemble material of one kind to impress on it the stamp of individuality, to give it life, the Vulcan required a specific assistant.This was the Archeus, and in Paracelsus' biological theories the Archeus assumed a leading position. " T h e Archeus directs everything into its essential nature." This it accomplished by the chemical process of separation. T h e

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Archeus "knows how to distill and to prepare according to proportion and distribution, just as the art in itself has power to do so by means of sublimating, distilling, and reverberating. For all the arts are present in man as well as in alchemy outside." Every individual process in life has its own Archeus and this is what makes an organism an individual. This idea of specificity is central to Paracelsus' thinking, and the mechanism of specificity is the Vulcan in the outer world and the Archeus in the living organism. 10 The physiological and medical theories of Paracelsus follow directly from the ideas mentioned above. T h e chief Archeus in man is the one which resides in the stomach. His function is to separate the nourishing parts of the food from the waste products. When digestion is normal, the food becomes liquid, the waste products remain solid and are eliminated. The nourishment passes to the other organs. Each of these selects that portion of the nutriment it requires, acting under the control of its Archeus. T h e stomach carries out the first alchemical separation for the general welfare of the body, the other organs for their own welfare. Each digests the food further, taking up the nutritive portion and separating off a waste portion which is eliminated by the "exit" characteristic of the organ: the lungs by coughing, the brain by nasal discharge, the kidneys by the bladder, and the heart through a "chaos," a term used rather vaguely by Paracelsus in a number of ways, but in this context representing a vaporous exhalation. When all these processes are proceeding normally, no residues are left, but if some of the wastes accumulate, disease results. Paracelsus was much interested in diseases in which calcified desposits accumulate at specific sites in the body. Such deposits he called "tartar," the name used for solid deposits in wine casks. In his view the tartar of the body was part of the waste portion of the food and so was an external material introduced into the body. Normally this was eliminated in the wastes, but at times, under the influence of excess salt, it was coagulated and precipitated at the specific site where digestion by a given organ was imperfect. In the mouth, where a preliminary digestion took place, it formed the tartar on the teeth. In the gallbladder and

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kidney it formed stones. In the lungs it caused the calcareous deposits seen in certain cases of tuberculosis. All these, and many other pathological conditions, Paracelsus called "tartaric diseases." In the case of plague he believed that the tartar in depositing carried with it a certain amount of arsenic which produced the specific plague symptoms. He thus adapted the Ficino theory to his own ideas. 11 As Pagel has pointed out, this generalization of the etiology of disease had a number of important implications.Disease is a distinct entity, exogenous in origin, due to chemical causes, specific in location, and caused by faulty metabolism. All these ideas set Paracelsus' view of disease completely apart from the older humoral theories and gave him and his followers a new impulse to investigate the causes and treatment of illness.12 The theory of the specificity of diseases and their localization in specific organs led Paracelsus to a new concept of drug therapy. He did not believe in the "complexions" of drugs, the Galenic idea that they contained varying degrees of the different qualities. As he remarked, "Names have no virtue; substances have." 13 Therefore he looked for new methods of discovering useful drugs. Since diseases come from the exterior, drugs to treat them should also come from the exterior. If a drug had the power to combat a specific disease, it had to contain a specific virtue or power, intrinsic to it, which Paracelsus called the arcanum. The arcanum ultimately came from the stars, transmitted through the air, which he here called the "chaos," into the elements acting as matrices for the three principles. These in turn made up the objects, in this case the drugs with their own arcana. The arcana then acted on organs or bodies generated from elements elaborated from the same astral influences as the drug. Here again the theory completely altered the type of drug sought. In the Galenic view the drug should counteract the harmful quality of the evil mixture of humors, and so the theory required that contraries should be used as drugs. In the view of Paracelsus, like cures like, and similarities rather than contraries were required. Some similarities could be found by looking for "signatures." T h e astral influences produced in the drug something which resem-

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bled the shape, color, or other property of the organ to be treated, and this would tell the physician what drug to use. Sometimes the drug might be so powerful that it acted as a poison. In this case, either the quantity administered might be reduced or by chemical treatment the power might be attenuated. Therefore the strength and dosage of a drug had to be considered carefully, another innovation in pharmaceutical practice. 14 An example of the value of chemical treatment is seen in his use of mercury compounds. Mercury itself was much used at the time in the treatment of the new disease, syphilis, which had only recently appeared in Europe. T h e extreme toxicity of the mercury vapors caused much trouble. Paracelsus converted mercury to the oxide and other compounds and found the safety and effectiveness to be much improved. In making his chemical remedies he introduced standardized methods of preparation which for the first time permitted generalization about chemical reactions. 15 At the same time he established the medical and pharmaceutical principles which in their development by his followers became the field of iatrochemistry, the use of chemical remedies for specific diseases. Paracelsus applied his chemical theories to other aspects of human biology. He decried the old practice of uroscopy, the visual inspection of the urine by the physician in an attempt at diagnosis. He believed that the alchemical procedures of extraction, coagulation, and distillation should be applied to urine to separate its amounts of sulfur, salt, and mercury. While these methods actually yielded very little practical information, they introduced the idea of the chemical examination of urine. 16 In the course of his obervations, Paracelsus noted the precipitation of albumin in the urine by acids, and the acidity of gastiric juice, though he believed such acidity represented an abnormal condition. 17 Paracelsus used the term "chaos" often, but in a number of confusing ways. In many cases he meant a substance or quality which altered the properties of the body containing it. Urine derived its color from the chaos residing in it. However, in most cases he thought it to be a special part of the air which communicated life to animate beings. It was dispersed through the human body and by violent movement might cause a disease. 18 Paracelsus rec-

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ognized that air was necessary both for combustion and for respiration, but he believed that the active portion, the chaos, was an astral emanation. T h e remarkable properties of saltpeter in gunpowder convinced him that this was a special kind of salt, and he thought there might be two kinds of stars, a nitrous and a sulfurous variety. T h e emanations from these, transmitted through the chaos, might interact in the macrocosm to produce thunder and lightning, and in the microcosm, man, might similarly produce burning disorders. These ideas were further developed by his followers into the concept of nitro-aerial particles in the air, and Debus has traced the development of this idea to the well-known theories of Mayow and Hooke which are considered forerunners of the oxygen concept. 19 The general position of Paracelsus in the development of biochemical concepts has been well summed u p by Pachter: "As a biochemist he asserted that man is made out of the same material as the rest of creation, feeds on the substances which make u p the universe, and is subject to the laws which govern their growth and decay. At the same time, each living being is unique, individually constituted, and follows his own destiny." 20 Most of the works of Paracelsus were not published until after his death, and so only those orthodox physicians who confronted him directly found it necessary to confute his violent criticisms of Aristotle and Galen. Meanwhile, however, even some of the orthodox Galenists were beginning to recognize certain weaknesses in the accepted theories and to propose modifications of them, while still maintaining as many features of the classical theories as they could. One of the weakest points in the older view was the explanation of digestion as due to coction of food in the stomach by innate heat. Agrippa of Nettesheim (1487-1535) pointed out that heat may digest, but simple exposure of food to heat does not produce the changes which occur in the stomach. To get around this difficulty he was forced to assume that there must be some occult virtue in the stomach to supplement the action of the heat. 21 The humanist Johannes Reuchlin (1455-1522) held that some specific property which was not heat was producing digestive action. 22 T h e noted French physician Jean Fernel (1497-1558),who first

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used the name physiology in its modern sense, 2 3 practically gave up hope of finding an explanation for digestion. He believed that the qualities and humors in the stomach were so mixed and combined that they could not even be comprehended. Hence he had to assume the existence of some occult power which performed the work of digestion. 2 4 Similar views were held by Bernardino Telesio (1509-1588), who believed that a great quantity of spirits directed digestion. 2 5 Fernel and Telesio, however, carried the analysis somewhat farther. They differentiated the biles of Galen into two species, one acrid, which produced effervescence when poured onto earth, and the other acrimonious, resembling the salt from wood ash (potassium carbonate). Thus these two fluids were acid and alkaline, respectively. They believed that these acrid and acrimonious fluids were harmful byproducts of normal digestion, but the seeds of Van Helmont's later theories of digestion can be seen here. 2 6 In the 1560's publication of numerous manuscripts of Paracelsus began to appear, edited by enthusiastic followers such as Adam of Bodenstein, who had been cured by one of the chemical remedies. T h e doctrines of iatrochemistry spread rapidly over Europe. 2 7 Thomas Erastus (1523-1583) issued a bitter attack on them in 1572, using language almost as violent as that of Paracelsus himself, 28 but this and similar attacks only helped spread knowledge of these works more rapidly. T h e vagueness and inconsistency of many of the writings of Paracelsus permitted a number of his adherents to make their own interpretations of some of his ideas, but the essential features, especially the belief in the three principles and the efficacy of specific chemical remedies, were common to all. Sulfur, mercury, and salt were now held to be the primitive materials out of which all matter was composed, and the four Aristotelian elements sank to an unimportant position. This was very clearly shown in the works of Joseph Duchesne, usually known by his Latinized name, Quercetanus (1544-1609), who based all his theories on triads. He took the three principles as basic, assumed the existence of only three elements, earth, fire, and water derived from them, and proposed three new humors

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in the body: chyle, venous blood, and "the nourishing h u m o r of life," which was f o r m e d by repeated circulations resembling a chemical distillation u n d e r the infuluence of the heat of the heart. This h u m o r circulated t h r o u g h the arteries to turn into bodily substance. 2 9 By the beginning of the seventeenth century, theories of bodily mechanism had become extremely confused. This was probably an important reason for the tendency of the iatrochemists to concentrate on the preparation of chemical remedies. In England this tendency was most strongly marked, and Debus has called it the Elizabethan compromise. 3 0 Physicians there accepted chemical drugs as they f o u n d them useful and disregarded the theoretical views which had led to their choice originally. O n the continent struggle was more intense, especially in Paris, where the conservative medical faculty led a violent resistance and m a d e a strong attempt to retain the Galenicals. However, the trend to consider the n a t u r e of actual substances rather than qualities and degrees could not be stopped. T h e position of the Paracelsians was strengthened by the fact that m o r e and more new c o m p o u n d s were being prepared. This is not surprising, for alchemists were learning the nature of chemicals d u r i n g this period. T h e r e was a close relation between alchemists and iatrochemists. O f t e n the same m a n carried on the activities of both. Interest in the new c o m p o u n d s themselves was accompanied by interest in their therapeutic properties. New metallic compounds were continually being described. A great interest began in derivatives of antimony, leading to the publication of such works as the Triumphal Chariot of Antimony by the pseudo-Basil Valentine in 1604 and the Anatomy of Antimony by Angelo Sala in 1617. 31 Chemical remedies began to a p p e a r in the E u r o p e a n pharmacopoeias. T h a t of Valerius Cordus (1546) listed none. By 1613 they were f o u n d in the Pharmacopoeia Augustana, a standard work. T h e first edition of the Pharmacopoeia Londinensis in 1618, in the writing of which the leading Paracelsian, T u r q u e t de Mayerne, took part, included a n u m b e r of such remedies. By 1684 they were fully accepted. T h e t r e n d initiated by Paracelsus had been well carried out by his followers. 32

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It is worth noting that iatrochemistry was essentially a qualitative science. There were iatrophysicists at this period, physicians influenced by the new discoveries of scientists such as Galileo, who were active in the mathematization of science. The iatrophysicists wished to do the same for medicine. They attempted to use mechanical models for muscular action, comparing the heart to a pump, the stomach to a churn, and so on. In some cases they achieved success, as in the measurement of the loss of weight due to insensible perspiration in the experiments on the balance by Sanctorius (1561-1636), published in 1614. The greatest of these discoveries was that of the circulation of the blood, announced in 1628 by William Harvey (1578-1657). However most of the attempts at quantization did not lead very far, since the qualitative background was not adequate. 33 On the other hand, many iatrochemists felt that they were approaching the secret of life by their studies. They often felt an aversion to the mechanical attack of the mathematicizers. Debus believes that their qualitative 'method was as important for the development of modern science as was the mathematical approach of the physicists.34 By the middle of the seventeenth century the time was ripe for a new synthesis of the confused Paracelsian theories. Such a synthesis was produced by Van Helmont.

9

The Transitional Seventeenth Century

During the seventeenth century theoretical biologists moved definitely away from the old humoral concept of body functions. New chemical discoveries and the revolution in astronomy and physics brought about by Copernicus and Galileo were reflected in the mechanisms they devised to explain these functions. T h e new anatomical discoveries following the work of Vesalius required that explanations be found not only for digestion and assimilation, which had been the main concern of those previously interested in physiology, but also for the circulatory, nervous, muscular, and respiratory systems. It was generally agreed by almost all the physiologists of this period that material substances were involved in all bodily actions, that is, in our terms, that they were biochemical processes. However, explanations varied depending on whether the scientist was interested more in chemistry or in physics. In the first half of the century this distinction in interest became clear. On the one hand, stimulated by Paracelsus, attention was centered on the chemical reactions which were assumed to explain biological

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mechanisms. O n the other, u n d e r the influence of Galileo and related thinkers, these mechanisms were explained in terms of the mechanical and mathematical laws which were being discovered. Iatrochemical and iatrophysical schools flourished, the one chiefly supported by the followers of Van Helmont the other by the adherents of Descartes. During the second half of the century, the distinction between the two schools became somewhat blurred. Supporters of each f o u n d it necessary to accept some of the ideas of the other. T h e result was that a wide variety of opinions and theories was expressed and a period of a p p a r e n t confusion set in. Yet this led to much excellent experimental work, and f r o m this the m o d e r n science of biochemistry gradually emerged. J a n Baptista Van Helmont (1579-1644) was a Belgian physician who devoted much of his life to chemical experiments and who was p r o u d to call himself philosophus per ignem, philosopher t h r o u g h fire, which essentially meant a chemist. In his early life he was a follower of Paracelsus, but later, on the basis of his own observations, he became more critical of his predecessor. Nevertheless, his ideas always showed the influence of Paracelsus' teachings. Van Helmont was deeply religious. At times he had ecstatic visions. H e could respond emotionally and enthusiastically to the mystical aspects of Paracelsian theory. At the same time, he adopted a rational and scientific view of chemistry. Much of his theory was based on firm experimental grounds. As a result, his philosophical system was characterized by the presence of both scientific and mystical aspects. This may explain the fact that he utilized the balance constantly in his experiments, implicitly recognized the principle of the conservation of matter, and usually applied quantitative reasoning to his laboratory work, although he rejected the mechanical and mathematical methods which Galileo and the contemporary physicists were applying in their scientific theories. Like them, Van Helmont rejected Aristotle, but not because he distrusted Aristotelian mechanics. Rather it was because he could not accept the all-inclusive universality of Aristotelian principles as an explanation of a world characterized by specificity and individuality. In his view, fire was not an element, since it was not a f o r m of matter. Earth also could not be an element, since it could be

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f o r m e d f r o m water by condensation. Van Helmont believed he had proved this by fusing sand and alkali together to f o r m water glass, which liquefied on standing in air. Addition of acid precipitated the original weight of "sand." T h e r e f o r e water was a f u n d a m e n t a l element. This he proved by his well-known willow tree experiment, originally suggested by Nicolaus of Cusa over a h u n d r e d years earlier. He planted a willow in a weighed a m o u n t of earth, watered it for five years, and f o u n d an increased weight of the tree of 163 pounds, while the weight of the earth remained unchanged. T h u s the tree had "proceeded out of the element of water only." T h e true elements were air and water, but air could not be changed, and so water was the element out of which everything was created. 1 This experiment was later repeated by Robert Boyle and described in his Reflexions on the Experiments vulgarly alledged to evince the 4 Peripatetique Elements or ye 3 Principles of Mixt Bodies, probably written in 1657 or 1658, 2 much of which was later incorporated in the Sceptical Chymist of 1661. Boyle described the repetition of Van Helmont's experiment by his g a r d e n e r under his direction, using a faster growing squash plant. H e also r e p o r t e d experiments on growing plants in water alone. 3 T h e latter experim e n t was probably suggested by his friend Robert Sharrock (1590-1684). a botanist who owed the idea to Francis Bacon. 4 It is clear that the original idea for all these experiments came f r o m Nicolaus of Cusa, t h o u g h neither Van Helmont n o r Boyle mentioned him by name. H o f f 5 believes that the dislike which both Catholics and Protestants came to feel for the ideas of Nicolaus may have caused a subconscious inhibition which prevented crediting him with the idea. At any rate, Boyle, while accepting the idea that living substance might arise f r o m water, could not follow Van H e l m o n t in considering water as the origin of inorganic substances. T h e work for which Van H e l m o n t is probably most famous was his identification and naming of gas. This he distinguished f r o m air, since it was contained in substances a n d could be liberated as a spirit, while air could never be changed. H e obtained gases f r o m a n u m b e r of d i f f e r e n t sources and knew that different gases had d i f f e r e n t properties. Although many of the gases he believed

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to be different were actually carbon dioxide from various sources, he also described formation of nitric oxide, impure chlorine, sulfur dioxide, and probably others. 6 He was the first to use the word "gas", deriving it from "chaos." Paracelsus had used the latter term, but not in the systematic and philosophical manner of Van Helmont 7 who gave to gas a leading place in his theories of the nature of matter. T h e specificity of gases fitted well into Van Helmont's basic idea of the specificity of substances and individuals. This had been an important part of the thinking of Paracelsus, and it was adopted completely by Van Helmont. He rejected the Aristotelian view that a living being was composed of mixtures of general qualities, common to all things. Instead, organisms were composed of seeds, active principles responsible for specific form and function. Water, at first an inert element, received the seeds of various materials such as metals or plants. In accord with his religious views, Van Helmont believed that th^ seeds were created by God to confer specific properties on the fundamental water to produce the individual substances which make u p the world. They were a primary "image" and "ferment" of the matter which was to be formed. "The image of the ferment impregnates the mass with the seed." T h e term "ferment" as used here signified to Van Helmont an active agent which carried out a vital or chemical process. It bears somewhat the same relation to his biological system that enzymes do in ours. As matter gradually took on its special characteristics it acquired a characteristic gas of its own. Here Van Helmont was influenced by his discovery of the different gases which were contained in solid bodies but could be liberated by fermentation, neutralization of acids by alkalis, combustion, and so on, in the form of "wild spirits." He used this term because the gases, once liberated, could not be contained in any of his laboratory vessels. He believed that every substance in nature contained its own gas, a spirit "coagulated like a solid body." 8 T h e importance of gas in Van Helmont's system was that it contained the essential specificity which is characteristic of nature. In man it was controlled by higher forces. He believed that in man there was an immortal soul which, before the Fall, had acted directly on an indwelling

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Archeus (the term taken from Paracelsus). Man at that time was immortal. After the Fall, man acquired a "sensitive soul" which was mortal and conferred mortality on him. The immortal soul then acted through the sensitive soul which now controlled the Archeus. T h e Archeus in turn acted through the ferments. 9 Life was a union of the Archeus, expressed as a gas, and the ferments which acted on it. T h e gas reverted to water when its seed was extinguished. In general, Van Helmont rejected the macrocosmmicrocosm theory and with it much of the astrology so common in his day. However, he could not escape this entirely, and he did admit that there was an emanation from the stars which he called "bias." It was transmitted instantaneously to earth by an allpenetrating force which he called "magnale"; it could affect air movements, winds, storms and to some extent, mankind. 1 0 These philosophical ideas, attempts to account for both the spiritual and the material aspects of life, formed the basis for the very practical theories of biochemical function which Van Helmont developed, largely as a result of his laboratory studies. He refused to believe that the innate heat of the Aristotelians could account for digestion of food or its change into body substance. It was too general. Food placed in warm places did not digest, it putrefied. Digestion was not improved during a fever. It was a specific function, differing in different species. T h e same food produced either different animals or a different organ in the same animal. Therefore in every case a specific ferment had to be employed to direct the digestion. In his youth Van Helmont had fed sparrows from his mouth and had noted an intense acidity in the throat of the birds. He had also seen that his glove was partly reduced to a fluid when soaked in an acid. He realized that gastric juice is acid, and is always so. Paracelsus had considered such acidity to be temporary and pathological, but Van Helmont recognized that acidity was necessary for normal digestion. He was the first to do so, and in doing it he made specific the "occult quality" which Fernel had declared needed for digestion. T h e quality was an acid. 11 Pagel believes that Van Helmont knew the acid was "spirit of salt," hydrocholoric acid. 12 Naturally, with his stress on the importance of specificity in life, Van Helmont believed that each species had its

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own stomach acid, a n d that this fact accounted for its food preferences. T h e vital factors in transforming foods were the various f e r m e n t s which acted on them. 1 3 T h e stomach, together with the spleen, as the first digestive system was given the greatest importance. T h e r e resided the Archeus influus, the directing force for the entire body. Digestion occurred in the stomach because of the acidity, which was supplied f r o m the spleen. However, Van Helmont distinguished six separate digestions that took place before the food became tissue. Following gastric digestion the pylorus, u n d e r the control of the Archeus, opened to admit the gastric contents to the d u o d e n u m , where, in the second digestion, the acidity was neutralized by bile f r o m the liver. This reaction, which produced the neutral salt sal salsum, for the first time introduced the chemical reaction of neutralization of acids by alkalis into biochemical thought. This, of course, was a materialistic theory, and Van Helmont was a vitalist. Hence the necessity arose for the introduction of the Archeus into the picture. 1 4 T h e chyle p r o d u c e d by the neutralization passed through the intestinal wall and was carried to the liver for the third digestion, which produced venous blood. This u n d e r w e n t a f o u r t h digestion in the heart, producing arterial blood. T h e fifth digestion gave vital spirit to the brain, and finally, suitable materials were assimilated into tissue substance in the various organs. 1 5 While innate heat was not responsible for these processes, Van Helmont recognized that it had an effect on the speed with which they occurred. T h e final digestion was very specific in each organ. Each had at its base a "kitchen" in which the Archeus insitus resided to direct solution of the food material brought by the blood and its conversion to the material of the tissue. For example, the "kitchen" pf the stomach was the spleen, that of the tooth, its root, that of the nail, its bed, and so on. 1 6 Solution was the most powerful effect produced as nature mastered matter, and Van Helmont devoted much e f f o r t to a search for the universal solvent, the Alkahest. However, in the body the various solutions were the result of the specific action of the individual ferments. If the ferments acted properly, solution was complete, and the organ was

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healthy, b u t if an "alien f e r m e n t " e n t e r e d f r o m outside, a r e s i d u e m i g h t be left which could lead to disturbances in either the a n a t o m y o r t h e f u n c t i o n of t h e o r g a n . T h i s would be a disease. T h u s diseases came f r o m specific causes, external, as Paracelsus h a d believed. So t h e old h u m o r a l theory of disease h a d to b e a b a n d o n e d . 1 7 Specific medicines with their own divinely given forces were r e q u i r e d in t r e a t m e n t . T h e use of iatrochemical r e m e d i e s was t h e r e f o r e to be e n c o u r a g e d . 1 8 While V a n H e l m o n t was developing both rational a n d mystic vitalistic doctrines, a m a j o r discovery was m a d e which could have been explained in mechanistic t e r m s b u t which was taken as a p r o o f of vitalism by its discoverer, William H a r v e y (1578-1667). I n 1628 H a r v e y published his De motu cordis et sanguinis a n d his description in this of the circulation of the blood gradually won acceptance. A l t h o u g h it r e p r e s e n t e d a complete break with t h e Aristotelian a n d Galenic theories, Harvey r e m a i n e d in m a n y respects a t h o r o u g h Aristotelian d u r i n g his life, in s o m e ways going even beyond Aristotle in vitalistic beliefs. T o him blood was the very essence of life, taking p r e c e d e n c e even over t h e heart. H e believed that blood contained an i n h e r e n t animal spirit which could n o t exist a p a r t f r o m the blood itself. W h e n blood was r e m o v e d f r o m the body it lost this spirit a n d became m e r e gore. 1 9 In fact, blood was a substance "whose action was soul." 2 0 T h i s spirit was not o n e of t h e material spirits of Fernel a n d certainly not t h e material animal spirit which Decartes, who knew of Harvey's work, subsequently assumed as t h e effecting mechanism of animal life. R a t h e r this concept of Harvey was related to t h e purely vitalistic theories of Stahl a n d his successors. T h e idea of spirits, vital, animal, o r rational, derived ultimately f r o m t h e concept of souls of t h e G r e e k philosophers, b u t by t h e seventeenth c e n t u r y these spirits h a d acquired a d i f f e r e n t a n d o f t e n varied significance. T h e t e r m was loosely used by almost everyone to express some f o r m of m e c h a n i s m by which the living body o p e r a t e d , b u t each individual i n t e r p r e t e d it in his own fashion. Sometimes a spirit was a mystic expression of a vital life force, sometimes it was a physical entity which obeyed the laws of mechanics a n d p r o d u c e d specific effects in accord with these laws. A n a d h e r e n t of the m o r e mystical concept was Sebastian Wirdig (1613-1687), w h o wrote A New Medicine of the Spirits in 1637. H e

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believed in a wide variety of spirits which controlled nearly all natural events and which could unite into one dominating spirit in the body. In m a n they could produce an acidity which caused disease and which could be controlled only partially by chemical remedies. Daniel Duncan of Montpellier in 1682 also discussed the doctrine of spirits moving t h r o u g h the nerves to excite flow of saliva, hearing, and even imagination. His spirits at least obeyed some of the laws of mechanics. 2 1 However, the idea of a completely mechanical controlling spirit was d u e to the great contemporary of Van Helmont, Rene Descartes (1596-1650). H e was one of the last philosophers who attempted to establish an entire cosmology and to explain all the facts of nature by logical deductions drawn f r o m his own f u n d a mental ideas. His starting point was his famous phrase Cogito ergo sum. In o r d e r to think, there had to be a res cogitans, mind, which could a p p r e h e n d its own thoughts, but which was entirely distinct f r o m the matter which constituted the physical universe. Matter had one basic property, extension. It occupied space. Mind did not. Matter followed the physical laws which had been expressed by Galileo and his fellow astronomers and physicists. Descartes fully accepted their mechanical view of the world. It was his aim to drive out all occult forces and o f f e r a mechanism which, once set going, would continue to function, r u n n i n g material events like a mechanical clock. Since he based his ideas on physics and mechanics, most of his theories fell in these fields, but in his desire for a universal cosmology he necessarily had to explain chemical and biological facts. Even here, as in the physical world, everything had to be accounted f o r in terms of motion and heat. Perhaps his greatest influence on chemistry came f r o m his particulate theory of matter. He did not believe in atoms and the void between them, but he did hold that originally large particles of what he called the third matter moved slowly a r o u n d in vortices, in close contact with each other. T h i s was the only f o r m of motion possible to them. As they rubbed together, they wore off finer particles of a second matter, more rapidly moving, and of still more minute first matter, which filled all the interstices between the larger particles. Size and motion accounted for most of the physical properties, and the shapes of the particles of third matter permitted compatible

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particles to combine into chemical compounds. Later, chemists took over these ideas to account for chemical reactions and used the idea of the smaller particles in developing concepts of imponderable fluids such as light, heat, electricity, and the ether. Descartes was equally mechanistic in his biological theories. Having stressed the distinction between mind and matter, 22 he proceeded to deny the existence of mind to all organisms except man. Animals were merely automata, like the clockwork figures so popular in his day. They felt neither pleasure nor pain. T h e body, even of man, was a machine, powered by the heat of the heart, fed by the food carried in the blood. These functioned to produce "animal spirits" which, however, were made of extremely fine particles obeying the physical laws of fluids. These spirits formed in the brain and from there directed all actions of the body in response to stimuli which they received. T h e distributing system consisted of the nerves. These were hollow tubes, through the centers of which ran very fine fibers. T h e fibers conveyed sensation from the surface of the body to the brain, which then discharged animal spirits through the hollow spaces in the nerves to produce movements of the body. 23 T h e essential difference between animals and man was that in addition to the animal spirits which operated his body, man possessed a rational soul. This was the mind, distinct from matter. It resided in the pineal gland, for which Descartes could find no other use, and which he therefore assumed formed the connecting link between the rational soul given by God and the mechanical machine which functioned as part of the cosmological scheme. This idea of a dualism between mind and matter has continued to the present day as a philosophical concept. T h e mechanical model of body function served as a basis for the iatrophysical school of physiologists who followed Descartes and competed with members of the iatrochemical school who followed Van Helmont. During the second half of the seventeenth century new anatomical discoveries were made at an increasing rate, and the growing custom of investigating organ function in living animals made possible the development of new theories of physiological mechanisms. The function of nerves, muscles, glands and the circulatory system now had to be considered. The new freedom for speculation led to a great variety of theories and a profusion of

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books, which laid the g r o u n d w o r k for a more scientific approach to biochemical problems. In 1656 T h o m a s W h a r t o n (1614-1673) described the duct of the submaxillary gland. H e believed that, though blood might bring some sort of material to the gland to make saliva, most of the material was supplied by the succus nerueus, a new term for the animal spirits which Descartes had believed the nerves to carry. Wharton held that this nerve juice either transferred some material substance to the gland, and was thus itself purified while the substance left the gland t h r o u g h its duct, or that something was removed f r o m the gland by the nerve, which was strengthened by the new addition. 2 4 A more correct explanation of glandular function was given in 1662 by Nicolaus Stensen (Steno) (1648-1686), when he described the ducts of the parotid and other salivary glands. H e realized that the material for glandular secretion was b r o u g h t by the arterial blood and given u p to the gland as the blood passed to the venous state. T h e function of the nerve was only to cause movement or secretion. 25 In 1664 Regner de Graaf (1641-1673) succeeded in isolating pancreatic juice, which he believed f r o m its taste to have an acid salt character rather than the slightly alkaline reaction which it actually possesses. Both Stensen and d e Graaf were pupils of the Leiden professor Sylvius and he incorporated their discoveries into his iatrochemical theories. Francois de la Boe, generally known by the Latin f o r m of his name, Franciscus Sylvius (1614-1672), probably did more to popularize iatrochemistry than any of his contemporaries. His ideas were expressed f r o m 1641 on, but he became most influential after his a p p o i n t m e n t as professor of medicine in Leiden in 1658. T h e r e he f o u n d e d a school whose representatives spread over most of Europe. He was essentially a teacher and p r e f e r r e d to theorize on the basis of analogies rather than to carry out extensive experimental investigations, but his ideas were so appealing that students t e n d e d to accept t h e m uncritically. 26 T h o u g h he took his main ideas f r o m Van Helmont, he rejected most of the religious and mystical aspects of the latter's thought a n d based his system strictly on the chemistry of his day. H e r e he drew u p o n the experimental work of J o h a n n Rudolf Glauber (1604-1670), one of the earliest industrial chemists and an inves-

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tigator who made extensive studies on the reactions of acids, bases, and salts. Glauber stressed especially the importance of salts, of whose composition he had a clear idea. 27 Sylvius was the more ready to accept the work of Glauber since he had been greatly impressed by Van Helmont's theories of the importance of neutralization of gastric juice by the alkaline bile with formation of a neutral salt. Sylvius believed that all action in the body could be explained by chemical reactions. He rejected the idea of a vital force which could distinguish bodily reactions from inorganic reactions in the laboratory. T o him, the most spectacular chemical reaction was the effervescence produced when acids reacted with carbonates, or the production of bubbles of gas when a fermentation occurred. 28 It was the effervescence which most struck him, and he thought that such effervescence caused most physiological effects in the body. 29 Since the product of a neutralization of this type was a salt resembling those that Glauber had studied, he was the more interested, and he based his physiological system on such reactions. In his theory of digestion he disregarded the acidity of the gastric juice which had been so important to Van Helmont and concentrated his attention on the fluids discovered by Stensen and de Graaf. He believed that saliva brought about the first state of digestion, chylification, or the preparation of the food for further treatment. He accepted the erroneous view of de Graaf that pancreatic juice was acid, and thought that the second digestion consisted in neutralization of acid pancreatic juice by alkaline bile, with effervescence. The fact that these juices did not effervesce when they were mixed outside the body was said to be because only in the body were they exposed to sufficient heat to produce this effect. Sylvius denied that dilution of the mixed juices by the chyle would interfere with the neutralization, comparing the reaction to the increased effervescence which occurred when dilute rather than concentrated oil or vitriol was poured on iron filings. T h e digestive effervescence separated the useful parts of food from the useless ones. 30 That portion of the bile not used in digestion returned to the liver and was then carried by the venous blood to the heart,

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where, in the right auricle and ventricle, it met chyle from the lymphatic blood and effervesced with it, producing a vital fire which ultimately converted the chyle into true blood. He believed that inspired air aided in this process, since it contained "nitrous and subacid particles" which "could condense the rarefied and boililing blood and so gently restrain its ebullition". 31 Sylvius applied his chemical ideas to other systems in the body. In the kidney some precipitation of solid mattter occurred in the blood, and the kidney filtered this out, leaving the filtrate in the form of urine. Even the animal spirits, so beloved of the physiologists of the day, were not mere hydrostatic fluids to Sylvius, but had chemical properties. When mixed with blood they could convert it to a more perfect state. 32 Sylvius carried his ideas into the field of pathology. Disease was due to an "acridity" produced by an excess of acid or alkali, and it was to be treated by substances of opposite character. Like most of the iatrochemists, he used many mineral remedies. 33 T h e ideas of Sylvius were taken over and sometimes considerably modified by his followers. The significance of pancreatic juice was denied by J. C. Peyer (1653-1712) and J. C. von Brunner (1653-1727), who removed most of the pancreas from dogs and found that they continued healthy, though Brunner noticed an increased excretion of urine in his depancreatized dogs. 34 John Colbatch in 1696 stressed the alkaline nature of diseases. He claimed that in scurvy the blood contained more particles of volatile alkali than when in a state of health, as well as some fixed alkali totally lacking in normal blood. This condition could be cured, as sailors had found, by eating acid fruits, such as apples, oranges, and lemons. 35 Here he was evidently drawing upon the observations of the English ship Daintie in 1593, when Sir John Hawkins thus cured his sailors of scurvy. In his report, first published in 1622 he remarked "that which I have seen most fruitful for the sickness is sower oranges and lemmons." John Woodall in his Surgeons Mate published in 1617 reported that the East India Company used lemon or lime juice on its merchant ships, though the British n^vy did not adopt this practice until James Lind published his Treatise on the Scurvy in 1753.36 Thomas Willis (1621-1675), one of the founders of the Royal

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Society in England, accepted the three elements of Paracelsus: sulfur, salt, and spirit (for mercury), adding to them the two passive elements water and earth. This five-element theory, first suggested by Sebastian Basso in 1621, later became very popular among many chemists. Willis thought that the animal spirits, which determined the form and figure of everything, maintained a sort of disagreement of sulfur and salt. Digestion was due to an acid ferment in the stomach which formed chyle with the sulf u r of the food, and this chyle effervesced in the heart, the salt and sulfur taking fire and producing a vital flame which passed to the brain, much as spirit of wine rises on distillation. Fermentation produced motion. Like Sylvius, Willis believed that air contained nitrous particles which by combustion produced the heat of the blood when the air reached it, since niter supports combustion. Animal spirits in the nerves came from the brain to produce action, a Cartesian idea. 37 However, the nerves were not hollow tubes along which the nerve juice flowed, but rather solid fibers along which the juice passed as wine passes along the stretched dry strings of a fiddle.38 Willis expressed the idea that in the blood some parts were continually being destroyed, while others were generated in their place, a sort of theory of the dynamic state of body constituents. 39 Soul consisted of the flame of the vital spirits in the blood and the light of the animal spirits in the brain. 40 Nathaniel Highmore (1613-1685) took a more Cartesian view of animal spirits as minute fiery particles which were rarefied by fermentation in the heart and then carried by the blood to the brain, from which they could move through the body, producing emotions. He held the old Greek idea that men are hotter than women and therefore contain more spirits. 41 All the preceding theorists clearly derived their main ideas from the Paracelsus-Van Helmont tradition, employing concepts of chemical action and fermentation along with varying degrees of acceptance of the older ideas of vital or animal spirits,to which different mechanical properties were assigned by individual thinkers. Such mechanical ideas stemmed from the influence of Descartes, but these men greatly diluted his purely mechanical theories. A further example of such modification of the physical theory can be found in the writings of some of the pharmaceutical

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chemists active at the Jardin des Plantes in Paris in the seventeenth century. They did not discuss theoretical chemistry in any detail, but they believed that the shape of particles of chemical substances determined their properties. Thus, Nicolas Lemery (1645-1715) thought that antimony compounds were emetics because their sharp points scratched the walls of the stomach, and that sleeping draughts had glutinous particles which, carried to the small vessels of the brain, condensed the spirits and modified their activity.42 Another group of workers reversed the emphasis, accepting a mechanical hypothesis almost entirely and making only minor concessions when their mechanical models were obviously inadequate. They made up the membership of the iathrophysical school. T h e chief exponent of this school was Giovanni Alfonso Borelli (1608-1679), professor of philosophy and mathematics at Messina and Pisa, and a member of the famous Academia del Cimento, which existed in Florence from 1657 to 1667 as one of the earliest societies devoted to experimental science. Borelli was essentially a mathematical physicist. He wished not only to explain all the functions of the body by mechanical principles, but also to measure them as far as possible. He made many calculations on the strength of muscles, the propulsive power of the heart, and similar physiological processes. For the last twenty-four years of his life he was engaged in developing his biological ideas, whcih were finally published after his death in his De motu animalium of 1680-1681. However, they had been generally known through his teaching for many years before they appeared in print. Borelli's ideas on nerve conduction resemble those of Descartes, but they are much more specific. He believed in a succits nerveus, a physical substance which flowed in the nerves in accord with the laws of fluid mechanics. He classified this juice into a nutritive part which supplied a vivifying force to the material brought by the blood, and a spirituous juice which was concerned with production of movement and sensation. These fluids, together with a seminal juice relating to generation and nutrition in plants and animals alike, were always corporeal and could not act at a distance. 43 A blow to a nerve was transmitted along it to the brain in the form of convulsions, undulations, or titillations. When the sensa-

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tion reached the upper part of the brain, the sensitive soul residing there was able to judge from the violence of the blow and the fashion and mode of motion what the object causing the sensation was. It could then direct the proper response. According to Borelli: "wherefore it cannot be conceived that nervous action can take place without some local movement of the nervous juice passing along the whole length of the nerve right to the brain." 44 Nerves were held to act on muscle when the nerve juice reached it and reacted with some substance in the muscle itself. Here Borelli had recourse to a chemical theory, since purely mechanical principles were not in themselves sufficient to explain the action he was discussing. T h e interaction of the material substances in nerve and muscle produced a fermentation or ebullition similar to that which occurred when spirit of vitriol was poured onto oil of tarter (concentrated potassium carbonate solution). He explained changes in muscle as follows: "In like manner we may suppose that thre takes place in the muscle a somewhat similar mixing from which a sudden fermentation and ebullition results with the mass of which the porosities of the muscle are filled up, thus bringing about turgescence and inflation." 45 It will be noted that Borelli believed that when a muscle contracts, it increases in volume. This was disproved by Jonathan Goddard in 1669, when he showed before the Royal Society that when an arm muscle contracts under water, the water level falls. This experiment was repeated by Francis Glisson (1597-1677), who has often been credited with its first performance. 4 6 T h e experiment indicated to Glisson that "the fibers are shortened by an intrinsic vital movement and have no need of any abundant afflux of spirits, either animal or vital, by which they are inflated, and being so shortened, carry out the movements ordered by the brain." 47 Borelli was not aware of this experiment when he wrote his book. Borelli showed, chiefly by experiments, that many of the older concepts of the Aristotelians, and even some of those of Sylvius, were incorrect. He inserted a thermometer directly into the heart and into other organs and found no difference in temperature between them and any other part of the body; thus it was not necessary to assume some special function for the heat of the

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heart. 48 He also showed that it contracted as did other muscles in the body, though his explanations for the apparently involuntary nature of its functioning were rather vague. 49 Impressed by the powerful muscles of the stomach and their crushing ability, especially in birds, he thought that the stomach acted simply to grind u p food into a fine powder, though he admitted that a corrosive liquid might also be present and might have some effect. A few of his more extreme iatrophysical followers refused even to admit the presence of this juice, holding that the only purpose of the stomach was to triturate the food into the mass known as chyle. 50 Borelli wrote of the secretion of urine and asked, "Who then would wish to think that the particles of blood are picked out, separated from the watery particles (of the urine) and placed in separate receptacles by some magnetic virtue or by some ferment, acting like a servant possessing eyes?" Instead he thought that the kidneys, acting as sieves, had two types of openings from the tubules, "one a venous one which by reason of its adjusted configuration receives the particles of the blood only, not those of the watery urine, and another, the proper vessels of the kidneys, the shapes of which are fitted for absorbing the particles of water, but not the particles of blood." 51 Another great advance of the seventeenth-century physiologists was in the field of respiration. T h e mechanics of breathing were better elucidated, and at the same time the participation of actual substances in the interaction between air and blood was recognized. The fundamental discovery was that of Robert Boyle (1627-1691), who showed in 1660 that when air was exhausted from a chamber by his air pump, a candle could not burn and an animal could not survive in the chamber. This proved the longsuspected analogy between respiration and combustion. Boyle, like Van Helmont, believed that air as such could not react with anything, and so he declared that some sort of effluvium was dissolved in air, and that this was what the animal required for life. 52 After Harvey's work on the circulation of the blood, it was recognized that the change in color from venous to arterial blood took place in the lungs, and many investigators suspected that some exchange of particles took place there. T r u e to his mechani-

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cal outlook, Borelli rejected such ideas, holding that entrance of air into the blood caused continual delicate oscillations which regulated all animal actions. 53 This view was not generally accepted, however. Robert Hooke (1635-1703), who had served as Boyle's laboratory assistant in the work with the air p u m p , continued to be interested in problems of respiration. In 1667 he p e r f o r m e d an experiment before the Royal Society which proved that the motion of the lungs was not essential to life. 54 A dog with the chest o p e n e d in such a way that the lungs could not move was kept alive by blowing air t h r o u g h the lungs with bellows. W h e n the action of the bellows was stopped, the d o g fell into convulsions, but immediately revived when air was once more blown in. It is of some interest that Hooke wrote to Boyle that he hesitated to repeat this experiment "because it was cruel" to the dog. H e a d d e d that "the enquiry would be very noble if we could in any way find a way so to stupefy the creature so that it might not be sensible." 55 A m o n g other experiments on the relation of air to life, Hooke showed that seeds would not germinate in a vacu u m , so that air was needed by plants as wells as animals. 56 Richard Lower (1632-1691) served f o r a time as assistant to T h o m a s Willis and may have originated many of the ideas usually ascribed to the latter. 5 7 In 1669 Lower published Tractatues de corde, in which he demonstrated that the color of venous blood was not altered until the blood passed t h r o u g h the lungs and that it assumed its bright color only after exposure to air. Repeating Hooke's experiment on the dog, he showed that as long as the lungs were supplied with fresh air, the blood "will rush out scarlet." H e concluded "wherever, in a word, a fire can b u r n sufficiently well, there we can equally well breathe." 5 8 It can be seen that in the latter half of the seventeenth century the idea was fairly widespread that some sort of nitrous particles must exist which were needed when combustion occurred, and that such particles must be present in air when something b u r n e d in it. T h e violent explosion of niter in g u n p o w d e r and its evident connection with combustion was probably the source of this idea. Partington has traced the theory to the writings of several authors prior to Mayow. 59 Guerlac has pushed the origin back to the writings of the alchemist Sendovogius (c. 1556-c. 1636). 60 Debus 6 1 has

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traced the concept to Paracelsus and his followers, especially Du Chesne at the beginning of the seventeenth century. All these writers associated combustion with the sulfur and niter of gunpowder, and assumed some sort of relation between the explosion of the latter, the p h e n o m e n o n of t h u n d e r and lightning, and the essential n a t u r e of nitrous particles and sulfur for life. However, the specific nature of the relationship between these two substances was far f r o m clear, and the theories of the various writers were not always consistent. T h e y were finally organized and placed on an experimental basis by the work of J o h n Mayow (1641-1679). Mayow accepted the five element theory which had been popularized by Willis, but he changed the n a t u r e and function of the five elements. H e took over the niter and sulfur of previous thinkers and m a d e them the active pair of elements. He called them nitro-aerial and nitro-sulfureous particles. T h e passive elements were salt, water, and terra damnata. Reaction came f r o m conflict of the two active elements, which were perpetually hostile to each other. All changes arose f r o m the mutual struggle when they met. Heat was produced by their conflict. 62 Physiological actions, like those in the inorganic world, were caused by this struggle. T h u s , muscular activity came when animal spirits, which he identified with nitro-aerial particles, descended f r o m the brain and met saline-sulfureous particles in the muscle. T h e resulting effervescence produced contraction of all muscles, including that of the heart. Similarly, the nerves conducted nitro-aerial fluid to the membranes of the stomach, where it mixed with the fluid secreted f r o m the blood to f o r m the f e r m e n t i n g substance in the stomach. A similar action produced the pancreatic ferment. 6 3 Mayow still a d h e r e d to the effervescence theory of Sylvius, but his originality lay in his emphasis on the importance of the nitro.aerial particles and his experimental evidence for their existence in air. His extended the studies of Boyle and showed that when an animal and a b u r n i n g candle were placed together in a closed space, the animal survived only a short time after the candle went out. If the animal was alone in the chamber it survived nearly twice as long. Some residual air remained in both cases. T h u s the animal and the candle competed for the same material. This

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showed that "air is a compound" and the residual air after removal of the nitro-aerial particles was different from ordinary air. It extinguished a flame, would not support combustion, and was not essential for life. Mayow was the first to show that a specific substance (our oxygen) existed as part of the air and was extracted from it by living organisms. It entered the blood from the lungs and then functioned as indicated above in producing animal heat and muscular and nervous action. 64 Recognition of the existence and action of oxygen thus implied did not come for a hundred years, chiefly because of the delaying effect of the phlogiston theory introduced by Stahl, but the work of Mayow was not entirely forgotten and served as a basis for later studies on respiration. The seventeenth century was a period in which conflicting theories of various schools struggled for recognition. Some of these schools opposed each other directly, but most thinkers refused to accept blindly the teachings of even recognized authorities, preferring to take what they wished from any available source to construct their own systems. The result was an apparent confusion from which, at first sight, little could be expected to emerge. Yet the guiding principles behind this confusion were sound, and they set biological science on its modern path. Biochemical speculations had always assumed the existence of material substances which carried on bodily functions, but they had tended to assume the occurrence and properties of such substances tailored to fit the requirements of a given theory. Now more and more material substances were actually being isolated and identified. If a substance could not be found which fitted into a theory, that theory became suspect. Experimental observations on living animals continually showed that certain unexpected processes occurred, and new substances had to be found to fit these observations. T h e idea of specificity as opposed to generalized reactions, introduced by Paracelsus and Van Helmont, changed the thinking of biologists. There was still much to be learned, and chemists and physiologists were seeking the new facts needed, but the methods of experiment and conceptualization had effected a radical change from the older ways of thinking.

10 Physiology Comes of Age

T h e confusion of theories of physiological function which characterized the seventeenth century was largely cleared up in the first half of the eighteenth. However, a sharp division arose between those who stressed the uniqueness of living matter and those who believed the body to be a mechanical engine. Vitalistic and nonvitalistic schools emerged. The first developed chiefly from the theory of animism of G. E. Stahl. T h e second stemmed from the work of Boerhaave and Haller, who succeeded in large measure in reconciling the iatrochemical and iatrophysical schools of the previous century. T h e dispute between vitalists and nonvitalists, however, continued for the next two centuries. Georg Ernst Stahl (1660-1734) graduated in medicine from Jena, where he was taught by the alchemically minded Georg Wolfgang Wedel (1645-1721). In 1680 the latter published a textbook of physiology which was essentially based on the ideas of Fernel, expressed nearly 200 years earlier. Wedel wrote of spirits, the effects of the stars, temperaments, and humors. Underwood called this work "Fernel in modern dress." 1 Although Stahl was well aware of contemporary advances of medicine, some of the mysticism of Wedel probably influenced his later writings.

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In 1694 Stahl was appointed professor of medicine at the University of Halle at the suggestion of his friend, Friedrich Hoffmann. Hoffmann and Stahl soon quarelled, and in 1716 Stahl accepted an appointment as physician to the King of Prussia in Berlin, where he remained until his death. Stahl had two major interests in life, chemistry and medicine, and he did his best to keep the two entirely separate. Nevertheless his essentially theoretical outlook led him to important generalizations in each field which profoundly influenced the thinking of large numbers of chemists and physicians for many years after his death. In chemistry he is noted for his systematization of the older ideas of a fire material responsible for all the phenomena of combustion and the rusting of metals. This was expressed in his theory of phlogiston, which has been called the first great generalization in chemistry. Phlogiston was the material of fire which escaped from a body when it burned. A metal consisted of its calx (the oxide) combined with phlogiston. When a metal formed its calx, it lost its phlogiston. In most respects the theory accounted well for the facts of combustion, since it actually simply reversed the correct view. Where it is known that oxygen adds to a body, Stahl assumed that phlogiston left it. Quantitative measurement of gain in weight of a calcined metal meant little to Stahl, who was more concerned with his theory than with laboratory practice. T h e plausibility and comprehensiveness of the phlogiston theory, as well as the lack of understanding of the role of gases in combustion during much of the eighteenth century gave the phlogiston theory a leading place in the thinking of chemists of the period. In his medical theories Stahl turned completely away from chemistry and all the chemical explanations of the iatrochemists. He considered that chemistry, physics, and even anatomy were of little importance to medicine. 2 They described only the outward forms of life but could not describe life itself. A dead body decayed, a living one did not. T h e difference lay in the soul. 3 T h e distinction between inorganic and living matter was to be found in the "ordered disposition" which the soul maintained. 4 Here Stahl returned to Van Helmont's concept of the sensitive soul (anima sensitiva). However, where Van Helmont had believed the soul operated through the Archei and the ferments, Stahl

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thought it acted directly on all bodily processes. This anima was an immortal principle which came from afar, conferring life and all the features which distinguish the living body from the dead one. At death it returned whence it came. 5 T h e only link between soul and matter was motion: "By motion, indeed, the soul carries on all its doings." 6 Temporal relationships and organization were the essence of life. Anima was a force immanent in the body. Motion was immaterial, like the anima, different from material matter. Thus immaterial anima caused an immaterial motion which affected material matter. 7 Motion explained many physiological processes. According to Stahl's doctrine of "tonicity," the soft tissues of the body alternately contracted and relaxed, impelling the blood through the body. Much body heat was derived from the friction of the blood as it passed through the blood vessels. Body heat also came from the motion of the lungs. He thus contradicted the old idea that the function of the lungs was to cool the heat of the heart. 8 In spite of his dislike for introducing physics into medical theory, Stahl was here using iatrophysical ideas, and, as Hall has pointed out, he could not avoid introducing some chemical ideas also into his picture. He believed the body to be composed of a mixture of a subtle earth, fat, and water. Well aware of the inability of fat and water to mix, he assumed that the earth mixed with the water to acquire a sticky consistency to which the fat could better adhere. This gave the body the flexibility it required for motion, but the inherent instability of the mixture required the action of the anima to maintain and renew it.9 He considered digestion to be a sort of putrefaction or fermentation. In his opinion fermentation was "an internal motion within a suitable fluid by which concrete particles of different kinds of matter in a loose state of combination are, through violent agitation together, subjected to friction and collision, as a result of which the bonds of the existing combination are torn apart and the separated corpuscles after having been worn by attrition are united together in a new, firmer combination." 10 This could occur in both living and nonliving bodies. However, digestion was a special case. He admitted saliva and pancreatic j-uce might be involved, though he denied that gastric juice contained either an acid or a ferment. He said: "The fermentation which takes place

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in the alimentary canal is not an ordinary fermentation such as occurs in a merely c o m p o u n d nonliving body, but a most special character is impressed on the change, impressed by the energy of the soul." 11 In keeping with his avoidance of introducing his chemistry into his medical theories, Stahl m a d e little application of the theory of phlogiston to his physiology. H e realized that with so much combustion going on in the world, a large quantity of phlogiston would have to be liberated into the kir. He believed that plants could absorb this phlogiston and combine it into their resinous and inflammable parts. 1 2 T h e r e f o r e air did not contain enough phlogiston at any one m o m e n t for a breath to supply it to the body. H e a d d e d : "This is a posteriori clear f r o m the fact that only a very little of the matter of phlogiston can be received into even a large quantity of air, even in a place where it is sufficiently collected, as when inflammable things are b u r n e d . However these things may be, these considerations, interesting perhaps to the curious, add absolutely nothing to medical practice and it is not meet to waste any more time on them." 1 3 T h e weight of Stahl's reputation smothered the theories of Mayow and delayed an u n d e r s t a n d i n g of the function of respiration for as long as the phlogiston theory prevented an u n d e r s t a n d i n g of the n a t u r e of oxidation. T h e doctrine of animism thus p r o p o u n d e d by Stahl had a longer life than the phlogiston theory. T h e latter was overthrown by the laboratory discoveries of the end of the eighteenth century, b u t animism, t r a n s f o r m e d into vitalism, continued to dominate the thinking of many biologists until nearly the present day. T h e continuation of the mystical doctrine of spirits, so common in previous centuries and adopted by Stahl in his theory of animism, was countered by the more mechanistic thinking of the other two major figures of the medical world of the early eighteenth century, Friedrich H o f f m a n n and H e r m a n n Boerhaave. Both were excellent chemists as well as p r o m i n e n t physicians, and both by their biochemical concepts directed the thinking of their followers into m o r e specifically chemical directions. Friedrich H o f f m a n n (1660-1742) was for most of his life professor of medicine at the University of Halle, where he was at

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first on intimate terms with Stahl. The later disagreements between the two men were probably as much a matter of difference in temperament as in medical theory. Stahl was interested chiefly in theory, and Hoffmann was a practical chemist whose studies of the composition of mineral waters employed many purely chemical tests, some of which are still used today. 14 Hoffmann agreed with Stahl in ascribing most physiological processes to motion. This motion, however, did not come from an immanent animal, but was a "virtue" or formative force imparted by God. Once imparted, it operated according to strictly mechanical laws.15 Hoffmann belonged essentially to the iatrophysical school of physicians. In distinction from Stahl he believed that the study of anatomy and physics and, to a lesser extent, of chemistry, could reveal most of the mechanisms by which the body operates. 16 Since the discovery of the microscope it had been possible to look more deeply into the structure of the living body, and Hoffmann, like other physicians of his day, was impressed by the fibrous nature of many of the tissues which were seen microscopically.17 Accordingly he believed that the fundamental anatomical structure was the fiber and that a number of such fibers, held together, made up the larger organs. T h e alternate contraction and expansion of the fibers caused systole and diastole of the heart, circulation of the blood, and most of the phenomena of life. 18 Still unable to discard completely the older doctrine of animal spirits, he felt that the ultimate cause of motion was to be found in two extremely fine elastic fluids. These originated in the omnipresent ether (a Newtonian concept), which was taken into the organism by respiration and was carried to the brain, where it broke down into nerve fluid and a residue in the blood. 19 These two fluids in true Cartesian manner obeyed the laws of hydrodynamics. Each produced its own effect. Blood in a vessel caused expansion by the mechanical effects of the fluid, abundance and heat. T h e fluid from the nerves by a "vital stimulation" caused the succeeding contraction of the vessel.20 Since blood produced such significant results, Hoffmann was led to a closer chemical study of this fluid and was impressed by its complex composition. He noted the coagulation produced in

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it by cold and likened this to the similar effect in gelatin. Thus blood had a "gelatinous nature," and foods with similar gelatinous properties such as meats were most suitable for forming blood. Here was an early recognition of the special character of proteins. He also observed that when four ounces of blood were heated, one ounce of solid matter was obtained. Therefore he drew the conclusion that the diet should contain three times as much liquid as solid matter to maintain the proper balance of the blood. 21 Perhaps one of the most intuitive aspects of his thought was his realization of the interrelationships of the parts and functions of the body. Changes in one organ or function, even though seeming slight in themselves, might bring about drastic changes in the body as a whole. There was a sympathy between different parts which related them to each other and to all body functions. 22 This is a thoroughly modern concept. Probably the most influential medical teacher of the early eighteenth century was Hermann Boerhaave (1668-1738), professor of medicine, botany, and chemistry at Leiden. His pupils spread his teaching over much of Europe from Vienna to Edinburgh. 2 3 He was one of the most careful and competent chemists of his day, and he carried out prolonged experiments with the utmost patience. For example, he distilled mercury 511 times and heated another mercury sample for fifteen years to see if the mercury could be changed by such treatment. It was not. Boerhaave leaned chiefly toward the iatrophysical school for his medical and physiological theories. He had no use for Stahl's animism and never mentioned phlogiston in his chemical textbook. It is not surprising that he recommended to his students the works of "the very ingenious Hoffmann," 2 4 since his ideas in many respects resembled those of Hoffmann, also an iatrophysicist. Boerhaave too believed that the ultimate building unit of tissue was the fiber, though he conceded that the fibers might in turn be composed of some sort of corpuscle. The fibers made u p the walls of the hollow vessels, beginning with the large blood vessels which led into successively smaller and smaller tubes carrying various types of fluids. T h e smallest tubes were beyond the range of the microscope but had to exist according to his system, which required a closed circuit for the flow of fluids. T h e only solid

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fibrils were those which m a d e u p the vessel walls. T h e body fluids flowing t h r o u g h the tubes contained various particles which were distributed by size according to the size of the tubes t h r o u g h which they could pass. T h e most obvious particles were the red blood corpuscles, first mentioned by J a n Swammerdam (16371680), though the actual priority and date of their discovery is not clear. They were rediscovered by Leeuwenhoek in 1673. 25 U n d e r the microscope Boerhaave saw these red corpuscles u n d e r going hemolysis when he a d d e d water to the blood. H e believed that each large globule was breaking u p into six yellowish globules which composed it. These in turn could break u p into six smaller pellucid globules which could pass into the smaller vessels. They were the constituents of special fluids such as milk or urine, which were secreted by special organs. 2 6 All these fluids, propelled by the heart, were in constant motion, obeying the laws of hydrodynamics. T h u s for Boerhaave, as it had been for H o f f m a n n , motion was the distinguishing mark of life. Bodily heat came f r o m the motion of the fluids. T h e finest and most subtle fluid was the nerve juice. When this juice was discharged into a muscle, it caused a contracton. Apparently the stimulus and response in the nerve were propagated by a shock wave traveling t h r o u g h the nerve juice. 2 7 In keeping with his iatrophysical tendencies, Boerhaave strongly attacked the acid-alkali duality advocated by his predecessor at Leiden, Sylvius.-Boerhaave carried out many experiments to show that body fluids such as milk and urine were neither acid n o r alkaline when fresh. 2 8 In particular h e opposed the idea that digestion was a process of effervescence. He surveyed the whole field of theories h e r e and d e n o u n c e d those which he felt were unacceptable. T h e weight of his authority and the definite nature of his critical statements did much to clear away a wide variety of older theories of digestion and assimilation, and though his own theories have not stood the test of time, they left only a single major theory to demolish instead of a large n u m b e r of competing ideas. T h u s , he a b a n d o n e d the "obscure and dubious hypothesis or postulata of a vital, innate, or digestive heat," an "acrid ferment," an "operating Archeus," the "false and imaginary . . . peripatetic qualities and galenic faculties," and "innumerable

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other false and pernicious hypotheses misleading from the truth." 29 This list certainly includes most of the older theories of digestion. Along with his studies of other bodily fluids, Boerhaave tested the reaction of the various digestive juices by taste, effervescence with substances of opposite character, and effect on the color of indicators such as syrup of violets, which is red in acids and green in alkalis. T h e use of the latter reagent had been popularized by Boyle. Boerhaave concluded that gastric juice was "a little saline, being neither acid nor alkaline." He probably made this observation on juice from a fasting stomach, and he thought that foods turned sour in the stomach soon after eating. He also considered bile and pancreatic juice to be neutral in reaction. Thus there could be no effervescence in the gastrointestinal tract. 30 The action of various foods in the stomach reflected their behavior outside the body. Most plant substances there, allowed to ferment in a warm place, produced an acid, while animal substances under the same conditions putrefied with formation of a volatile alkali (ammonia). This, of course, reflects the differing behavior of carbohydrates and proteins. Boerhaave was observing protein reaction when he concluded that white of an egg and blood serum were of nearly the same nature. T h e existence of chemical classes was beginning to be recognized. 31 Boerhaave's ideas on the distinction between carbohydrates and proteins were developed even more clearly by his follower, Iacopo Bartolomeo Beccari (1682-1766), professor of chemistry and philosophy in the University of Bologna, in his discussion of gluten in the treatise On Wheat (1745). T h e preparation of gluten from wheat flour had long been known. Partington 32 states that it was first prepared in 1665 by F. M. Grimaldi, but Browne 33 says that Du Chesne (died 1609) was "one of the first" to prepare gluten by working up a paste of flour with his fingers under a stream of water. Du Chesne described it as "a tenaceous, waxy, decidedly glutinous substance." Beccari, repeating this method of preparation, noted that a whitish material which was evidently starch was washed away while the gluten remained undissolved. He called the two fractions the amylaceous and the glutinous. Applying the method of Boerhaave (whom he mentioned

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repeatedly and admiringly) he showed by fermentation or putrefaction and also by dry distillation that the amylaceous portion yielded an acid spirit while the gluten gave an alkaline uriniferous substance. Thus starch was a vegetable material, and gluten, though formed by a plant, was an animal material. Since it came from plants it could be used directly by herbivorous animals to form their tissues. Beccari later studied the amount of gelatinous substance in broths prepared from various animal tissues. He believed that the more gelatin they contained, the more nutritious they were. The best gelatin came from a broth made from snakes. 34 A specific protein chemistry was emerging. Some workers began to feel that biological substances could be classified by chemical means, but their attempts to do so failed, since not enough chemistry was yet known. 35 Boerhaave applied his theory of plant and animal foods to the problem of assimilation. He concluded that plant products which at first were neutral but could become acid by fermentation could be called "acescent," while animal products were "alkalescent." Vegetable foods therefore had to become "animalized" before they could be utilized in the animal body. This process of animalization should be studied with chyle, the milky fluid observed in the intestine. Chyle was hard to obtain, and so he studied milk, which he considered to be a somewhat perfected chyle which could still become acid on standing. Alkalinization by the animal took place under the influence of the heat which came from the friction of moving body fluids. Thus, as Jevons says, "the proper assimilation of food came to depend, like most things in the body, on the proper functioning of the vascular system and an important link was forged between the chemical and mechanical viewpoints." 36 This theory left the function of the stomach to be explained. Here Boerhaave inclined toward the mechanical ideas of Borelli. Mechanical pressure and trituration of the foodstuffs were important parts of chylification, though some putrefaction might be the result of action of the gastric juice. An incipient fermentation or putrefaction impressed the primary principle of vitality on the chyle. 37 Completion of assimilation occurred in the lungs, for through them all the blood flowed, while other organs received

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only part of it. Chyle b r o u g h t to the lungs received there "that degree of fluidity and attenuation which fits [the particles] to circulate freely t h r o u g h all the smallest vessels." T h e food particles were mechanically compressed into a configuration "suitable to compose all the solid and fluid parts of the body." As particles of the vessel walls were carried away by the fluid flowing t h r o u g h them, the vacant spaces thus created were filled with fresh particles of the right character b r o u g h t by the fluid f r o m the lungs. 3 8 A f u r t h e r problem facing anyone attempting to set u p a general system of body mechanics was that which had c o n f r o n t e d Paracelsus and Van Helmont, the need to account for biological specificity in the midst of generalities. Boerhaave solved this problem by his doctrine of the spiritus rector. This governing spirit was very subtle and volatile and was retained in its p r o p e r location by combination with a tenacious oil. Every individual, plant or animal, possessed its own spirit and derived its special individuality f r o m it. T h e spirit could be separated f r o m the oil by distillation, or even by shaking with water. For example, when cinnamon bark was distilled with boiling water, its spirit passed into the distillate as the odor, while the residual bark a p p e a r e d unchanged. T h e spirit of many plants accounted for their medicinal virtues. Dogs were able to track an individual because of the latter's spiritus rector.39 Boerhaave m a d e many experiments on body fluids. In the course of his studies on urine he isolated urea for the first time. His method well illustrates the patience with which he worked. He evaporated fresh urine to a creamy mass which he filtered while it was hot. T h e thick filtrate was kept in a covered vessel for a year. T h e salt mass which separated on the bottom was washed with cold water, dissolved in warm water, and purified by repeated filtrations. T h e solution was then concentrated by gentle heat until a solid began to separate. W h e n the liquid was cooled, the urea separated as little salty lumps like sugar crystals, odorless and not alkaline. This was "the natural salt of urine." 4 0 Boerhaave was careful to discuss all his biochemical studies in his medical courses and to demonstrate many of the properties of urine, milk, egg white, and blood serum. T h e second volume of his famous Elementa chemiae, which was long the favored chemi-

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cal textbook of Europe, contained lengthy sections on vegetable and animal chemistry. Lindeboom rightly says that he introduced biochemistry into medical teaching. 4 1 Like most of his contemporaries, Boerhaave believed that air was an elastic element which could not enter into chemical reactions, though he did admit that it might have a certain occult virtue which was the secret food of life. H e said of this food that he did not know "what it really is, how it acts, and what exactly it brings about," and he exclaimed, " H a p p y the m a n who discovers it!" Lavoisier later suggested that Boerhaave may have changed his ideas on the behavior of air on reading Hales' Vegetable staticks, which a p p e a r e d in 17 27. 42 His later works show little evidence of this, however. Stephen Hales (1677-1761) was an English clergyman who devoted much of his time to scientific experiments. In the work mentioned above he described heating a large n u m b e r of plants and recovering f r o m them varying amounts of "air." English scientists of this time did not accept Van Helmont's term "gas," and d u r i n g the whole period of the development of pneumatic chemistry in the eighteenth century they spoke only of "airs." It was in the course of his work with plants that Hales developed a practical f o r m of the pneumatic trough which m a d e many of the later studies of gases possible. 43 Hales demonstrated conclusively that airs could be combined in solids, liberated f r o m them, and recombined by suitable manipulations. H e did not distinguish between the different kinds of "airs" which he obtained. H e merely said that "air abounds in animal, vegetable, and mineral substances and by its presence somehow 'leavens' them." Such air was "fixed" in the substances in which it was bound. Physiology assumed a position as a science in its own right chiefly because of the work of the Swiss anatomist, physiologisi, botanist, poet, and novelist, Albrecht von Haller (1708-1777). Haller had been a student of Boerhaave, f r o m whom he derived many of his scientific ideas. However, he went far beyond his master in his emphasis on experiment. In 1736 he began teaching at the University of Göttingen, and there in 1747 he published his textbook, Primae lineae physiologiae, in which he e x p o u n d e d his physiological ideas. T h e book went t h r o u g h several editions and

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was translated into English by William Cullen. 4 4 I n 1757 Haller retired to his native B e r n e , w h e r e h e completed his m a j o r work, the eight-volume Elementa physiologiae corporis humani (Lausanne, 1757-1766), in which h e p r e s e n t e d a detailed account of his e x p e r i m e n t a l work a n d t h e conclusions h e d r e w f r o m it. Like Boerhaave, h e carefully a n d critically reviewed t h e work of all his predecessors, a n d even m o r e t h a n B o e r h a a v e h e was i n s t r u m e n t a l in causing elimination of a p r o f u s i o n of earlier theories which lacked s o u n d e x p e r i m e n t a l s u p p o r t . Later physiologists a n d chemists were thus able to base their work o n a m o r e o r less unified set of principles established by these leaders of e i g h t e e n t h - c e n t u r y t h o u g h t . Haller insisted on e x p e r i m e n t a l evidence f o r all t h e ideas which h e or his students p r e s e n t e d . T h e n u m b e r of e x p e r i m e n t s they carried o u t was e n o r m o u s . Haller's philosophy was s u m m e d u p in a statement f r o m his p a p e r o n t h e irritability of bodily tissues: " B u t the theory, why some parts of the h u m a n b o d y are e n d o w e d with these p r o p e r t i e s while others are not, I shall n o t m e d d l e with. For I a m p e r s u a d e d that the source of both lies concealed b e y o n d t h e reach of t h e knife a n d the microscope, b e y o n d which I d o not chuse to h a z a r d m a n y conjectures, as I have n o desire of teaching what I a m i g n o r a n t of myself." 4 5 Haller accepted t h e older idea of t h e i m p o r t a n c e of fibers as structural elements of t h e body. T h e s e fibers were e m b e d d e d in "cellular" material which s u p p o r t e d t h e m . T h i s material contained o p e n spaces which were interconnected t h r o u g h o u t t h e body, a n d in t h e spaces was "a watery vapor, gelatinous a n d somewhat oily, exhaled o u t of t h e the arteries a n d received again into t h e veins." Sometimes t h e oily material was c o m p a c t e d into fat. 4 6 It is possible to see in t h e ideas of Haller a b e g i n n i n g recognition of t h e chemical composition of t h e h u m a n body in relatively m o d e r n terms. Biological thinkers u p to this time a n d in some cases f o r long a f t e r w a r d t e n d e d to think of t h e s e p a r a t e body fluids such as chyle, blood, o r t h e digestive juices as specific in t h e m selves, little appreciating the chemical complexity of these substances. I n the absence of chemical knowledge this was t h e only a p p r o a c h possible. Now, however, not only physiology b u t also chemistry was b e c o m i n g a n i n d e p e n d e n t science with its own

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laboratory methods. Physiologists and chemists developed characteristic ways of thinking. Haller still thought as a physiologist, but he realized that certain classes of substances could be distinguished in biological fluids. T h e chemical processes he used were still based on distillations, but some of his conclusions went beyond those of his predecessors. T h u s , he described the coagulability of blood and noted that it contained a quantity of "sea salt" which could be detected by taste and sometimes seen u n d e r the microscope. H e continued, "That there is earth in the blood is demonstrated f r o m nutrition, and f r o m a chemical analysis, whereby the earth appears to lodge in the most fluid and especially in the oily parts of the blood. By some very late experiments, it appears that a considerable quantity of Ferruginous earth, easily reducible into metal by the addition of phlogiston, is contained in the blood when calcined." He knew of the work of Hales and that air could exist in combined ("unelastic") form. T h u s he stated: "Lastly, a n o t h e r part in the blood is air in an unelastic state and that in very considerable quantity; the existence of which air in the blood and serum is proved by their putrefaction and distillation, or by removing the ambient air f r o m them by the p u m p . But we do not think f r o m hence that the blood globules are bubbles full of air, for they are specifically heavier than the serum." 4 7 H e recognized that atmospheric air contained a "subtle element" which could penetrate the blood" 4 8 and by the action of respiration this air could be vitiated and r e n d e r e d unfit either for inflating the lungs or for supporting a flame. Such air had lost its elasticity. 49 Haller believed the seat of the soul lay in the medulla of the brain, where the nerves took their origin, and f r o m which a nerve juice flowed t h r o u g h the hollow nerves to the muscles. 50 This juice was an element of its own kind, unlike anything else, too subtle to be grasped by the senses, so that it could be known only by its effects. However, it was more gross than fire, or ether, or electric or magnetic fluids, since it could be contained in channels and restrained by the body; moreover.it was clearly produced f r o m a n d nourished by food. 5 1 It will be noted that this was an application to a physiological problem of the theory of elastic

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fluids which was increasingly influencing the thinking of eighteenth-century physicists. They were coming to regard heat, light, or electricity as imponderable flowing fluids with much the same set of properties which Haller ascribed to nerve juice. Therefore some thought nerve juice and electrical fluid were identical. This Haller denied, since nerve juice was of the nature of food, from which it arose, and electricity was not. 52 Haller then raised the question of what became of the nerve juice after it had been poured out onto the muscles to produce sense and motion. He concluded that it was exhaled, probably through the cutaneous nerves. 53 Haller was especially noted for his theory of irritability and sensibility of tissues. He derived this idea from Glisson, who had considered that all fibers in the body could expand or contract. Such motion, which Glisson called "irritability," in his opinion applied to and explained all bodily functions. This was for him a philosophical idea, since he proposed it before the microscope made structural fibers visible.54 Haller, however, could see the fibers, and he restricted the concept of irritability to fibers of muscle only. He felt that any tissue which contracted in his experimental animals when it was stimulated was muscular and irritable. On the other hand, the nerves which produced pain when stimulated were sensible tissues. Thus the nerve juice, produced in sensible tissues, was the stimulus for irritable muscle tissues. This doctrine had a long subsequent history. 55 Haller's theories of digestion and assimilation were derived from those of Boerhaave. He accepted the classification of foods as acescent and alkalescent and recognized that animal flesh belonged to the alkalescent type which had to be tempered and moderated by acescent vegetable foods. However, the fleshy foods contained a gelatinous lymph which could change spontaneously into blood. Food in the mouth was broken u p mechanically. T h e stomach contained no particular ferment and no acid acrimony "when it could be had pure from the food." 56 T h e only action of the stomach was to macerate, soften, and dissolve fibers and cellular bands, leaving a soft pulp. If food stayed too long in the stomach, it putrefied. 5 7 Pancreatic juice was watery, neither acid nor alkaline. Its function was to dilute the viscid chyle from the stomach, mitigate its

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acrimony, and mix with the food. 58 Haller had a very correct idea of the function of the bile. It was "extremely well adapted to dissolve oily, resinous, or gummy substances." It was "a natural soap; but of that sort which is made from a volatile saline lixivium, mixed with oil, and has water along with it. This, therefore, being intermixed with the aliment, reduced to a pulp, and slowly expressed from the stomach by the peristaltic force of the duodenum and pressure of the abdominal muscles, incorporates them all together; and the acid or acescent qualitites of the food are in some measure thus subdued, the curd of milk is again dissolved by it into a liquid, and the whole mass of aliment inclined more to a putrid alkalescent disposition; it dissolves the oily matters, so that they may freely incorporate with the watery parts and make up an uniform mass of chyle to enter the lacteals."59 T h e final form of the chyle resembled an emulsion composed of vegetable farina with animal lymph and oil. It was most similar to milk, into which it could most easily be converted. 60 Finally the chyle "mixed with blood, after it has circulated near 80,000 times through the body, fomented with heat, and mixed with a variety of animal juices, it is at length so changed that a part of it is deposited into the cellular substance under the denomination of fat; a part of it is again configured into the red blood globules; another part, that is of a mucous or gelatinous nature, changes into serum; and the watery parts go off, in some measure by urine, in some measure exhaled in perspiration; while a small part is retained in the habit to dilute the blood." 61 Thus in the theories of Haller we find a primitive recognition of the existence of the three major classes: proteins, carbohydrates, and fats, together with their different treatment and function in the body. It remained for the chemists to clarify and explain these concepts. During the second half of the eighteenth century the division between vitalistic and nonvitalistic physiology became pronounced, just as had been the case with the division between iatrochemistry and iatrophysics in the seventeenth. As in that case, the division was seldom absolute, since the vitalists usually looked for specific bodily mechanisms, even if these were caused by some unexplainable vital force, while the nonvitalists usually did not deny that some sort of distinction between living and nonliving matter might exist.

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T h e animism of Stahl gave birth to a number of different views of life processes. T h e term vitalism was especially popularized by Paul Joseph Barthez (1734-1806), who practiced medicine in Paris and taught for a time at Montpellier, which was a center for vitalistic thought. Barthez accepted Stahl's view of body and soul as the cause of life, but he added a third factor, the vital principle, which acted with or without the concurrence of the soul. At death the body returned to earth, the soul to God, and the vital principle to the universal principle of the cosmos. 62 It was this theory of the vital principle which distinguished vitalism from animism. Meanwhile experimental physiologists continued the work of Haller. Particular attention was paid to the digestive juices. Rene' Antoine Ferchault, Sieur de Reaumur (1683-1757), among numerous other scientific works, studied the digestion of various birds. T h e most important part of his work, published in 1752, involved feeding a kite various types of food in small metal tubes, covered at the ends with wire gauze. After a period of time the kite ejected the tubes, and Reaumur was able to study the partly digested food in the tubes or the gastric juice itself. He noted that bone was dissolved, meat was partly digested, and starch was not affected. He concluded that digestion was not putrefaction. T h e gastric juice was acid. 63 Lazaro Spallanzani (1729-1799) made numerous experiments on animals and men, noting digestion at various stages. He saw that gastric juice could digest foods outside the stomach. He believed that the juice was not acid itself, but that subsequent to its secretion it could become acid by some abnormality. Digestion was not putrefaction, since it did not resemble the putrefaction of meat left in pure water. Spallanzani was responsible for the first chemical analysis of gastric juice, which was carried out in 1777 by his colleague, the chemist Scopoli of Pavia. His report stated that the juice consisted of "pure water, saponaceous and gelatinous animal substances, sal ammoniac, and an earthy matter which exists in all animal fluids. It precipitates silver from nitrous acid and forms luna cornea [silver chloride]. This phenomenon might induce us to suppose that common salt exists in gastric juice, but the salt contained in this fluid is not common salt, but sal ammoniac." 64

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Various workers from time to time did note the acidity of gastric juice, especially in nonfasting animals. These included John Hunter in England and Bassiano Carminati in Italy. 65 However, no one at this time accepted acidity as an essential property of gastric juice. T h e reluctance to recognize this property probably arose from the fact that physiologists had for a long time been concerned with direct observations on effervescence, putrefaction, and fermentation and their relative importance in physiological processes. Acidity was a secondary factor in these discussions and relatively little attention was paid to its presence or absence. T h e characteristic difference in thinking of chemists and physiologists at this time is well illustrated here. Physiologists observed the phenomena occurring in the animal body and tried to account for them by mechanisms analogous to those known or observed in similar cases. When they needed to fit some material substance into their general theory, they simply assumed that it must exist and have the desired properties. This approach was specifically described by Frangois Boissier de Sauvages de la Croix (1706-1767), who pointed out that mathematicians used unknown quantities, χ and y, to set up their problems. Physiologists too should assume unknowns when required, in the hope that eventually these would become known. 66 This method is the opposite from that usually employed by chemists, who isolate and characterize the specific compounds they find in mixtures and then try to find a mechanism for their function in terms of the properties of the substances which have been found. During most of the eighteenth century chemists had not prepared enough substances to permit them to utilize this procedure, while physiologists had advanced their science to a point at which they could employ their method freely. However, just as physiology had flowered in the early years of the eighteenth century, so chemistry flowered in its later years. By the end of the century chemists had developed analytical methods and preparative procedures to a point at which they could begin to determine the ultimate constituents of body fluids and tissues. Physiologists and chemists continued to think in their own ways, but by combining their results, a true science of physiological chemistry could begin to emerge. It is therefore necessary to follow the advances of chemistry at this period.

11 Pneumatic Chemistry and Its Biological Significance

T h e major chemical development of the second half of the eighteenth century was the discovery of a whole new class of substances, the gaseous elements and compounds. The early work of Van Helmont on his "wild spirit" and the studies of Mayow and Hales on "sirs" had shown the existence of a definite substance, an elastic fluid, of which the ordinary atmosphere was composed. It was generally believed that this was one material which had to be characterized by its physical properties, since it could not react chemically. Differences in color or odor in different samples of air were due to the presence of accidental impurities. However, air might be "fixed" in solid bodies more or less mechanically. Such views were completely refuted by the discoveries of the new pneumatic chemistry. These discoveries also made it possible to explain and generalize the great physiological problems of the nature of respiration and the cause of animal heat which had long baffled physicians and physiologists. T h e fundamental basis for the new chemistry lay in the famous inaugural dissertation of Joseph Black (1728-1799), "On the Acid

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Humour Arising from Food and Magnesia Alba." 1 This appeared in 1754, and his detailed account of his chemical experiments on the subject was published in 1756.2 T h e work was begun because of Black's theory of digestion, which was essentially that held by most contemporary physicians. Black accepted the fact that plant foods tended to ferment to acids, while animal foods putrefied to alkaline products. He believed that normal digestion came from a balance in the diet of the two contrary kinds of food, "so that the chyle, made up of liquids so opposite to each other, cannot turn out to be of either kind; but retains its mild character for some time until it is carried into the stream of the blood." 3 When this process was distrubed and too much fermentation took place, excess acid was produced and many harmful symptoms resulted. The best remedy for this condition was magnesia alba (magnesium carbonate), and by the study of this substance Black was led to his famous experiments on mild and caustic magnesia and lime (magnesium and calcium carbonates and hydroxides). Black's experiments and conclusions and their effect on chemistry have been effectively summarized by Cranston. 4 His most significant result for the development of biochemistry was the demonstration that magnesium and calcium carbonates could be converted to their oxides with loss of gas which had previously been fixed in the salts, and so could be called by the name earlier suggested by Hales, fixed air (carbon dioxide). It is important to note that Hales had no concept of a specific gas which was a definite chemical substance. Black showed by the use of the balance that his fixed air combined in definite proportions with the metallic element. As an incidental observation he noted the insolubility of calcium carbonate in water and its precipitation when fixed air was blown into lime water. This reaction became the standard test for the presence of fixed air. By it Black proved that the air exhaled in respiration was fixed air. The sequence of quantitative experiments by which Black demonstrated his reactions was as follows. Heating magnesium carbonate gave magnesium oxide. The decrease in weight was due to the loss of a volatile and non-condensing material, which therefore had to be an air. T h e oxide dissolved in sulfuric acid to give Epsom salt. A solution of this salt was treated with potassium carbonate and the original amount of magnesium carbonate was

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formed. T h u s the carbonate was produced f r o m magnesium oxide by uptake of an air. A chemical reaction between a solid and a gas must have occurred, and it could be followed quantitatively. T h e old idea that there is only one air and that this air could not react chemically was completely overthrown. J o h n Robison in an 1803 biography of Black pointed out the impact of this discovery on the thinking of contemporary chemists: "What could be more singular than to find so subtile a substance as air existing in the f o r m of a h a r d stone, and its presence accompanied by such a change in the properties of that stone? . . . What bounds could reasonably be set to the imagination, in supposing that other aerial fluids, as remarkable in their properties, might exist in solid f o r m in many other bodies?" 5 Discovery of new gases now followed quickly. H y d r o g e n had been p r e p a r e d in an i m p u r e state by a n u m b e r of other early workers, b u t it was first purified and carefully characterized by Henry Cavendish (1731-1810), who at first believed it was p u r e phlogiston. Nitrogen was p r e p a r e d by Carl Wilhelm Scheele (1742-1786) and by Cavendish, but they did not publish their results, and credit for its discovery in 1772 is given to Daniel R u t h e r f o r d (1749-1819), a student of Black's. T h e crowning achievement of the pneumatic chemists, the isolation of oxygen, was carried out by Pierre Bayen early in 1774, though he did not recognize what he had done, and by Scheele even earlier, though he did not publish his results until 1777. T h e chief credit belongs to J o s e p h Priestley (1733-1804), who on August 1, 1774, decomposed mercuric oxide by the heat supplied by a large b u r n i n g glass. Priestley had begun his scientific career by publishing a History of Electricity in 1767. Even in this work h e mentioned that he had read and had f o u n d by his own experiments that "a candle would not b u r n in air that had passed t h r o u g h a charcoal fire or t h r o u g h the lungs of animals." 6 T h u s even before his attention was directed toward gases he was aware that there was a relation between combustion and respiration. Later he lived next d o o r to a brewery where carbon dioxide was given off in large quantities a n d he became interested in the properties of fixed air. As a result of his experiments with this substance, he invented soda water.

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He adapted a technique for collecting gases over mercury instead of water originally developed by Cavendish. This enabled him to isolate a number of water-soluble gases such as hydrogen chloride which had not been prepared before. In 1772 he made a major discovery when he obtained "nitrous air" (nitric oxide) by the action of nitric acid on various metals. He discovered that in ordinary air this was converted to a brown gas (nitrogen dioxide) which was soluble in water. T h e amount of this gas which formed was equivalent to the ability of ordinary air to support the burning of a candle or the life of a mouse. Therefore,Priestley felt that be had discovered a method for measuring the amount of air "fit for respiration." 7 When he discovered oxygen, Priestley found that mice lived longer in it and that it combined with more nitrous air than was the case with "common air." He concluded that it was "between four and five times as good as common air." Priestley was a firm believer in the phlogiston theory throughout his entire life, and he explained all chemical phenomena in terms of phlogiston. He thought that when the brown gas was formed, the nitrous air was losing phlogiston to another substance. Since his new air took up so much phlogiston, it itself must lack this substance, and so he called oxygen "dephlogisticated air." 8 He accounted for respiration by assuming that the organism took a large amount of phlogiston into itself with its food and this phlogiston became a waste product which had to be eliminated. T h e blood carried it to the lungs where, by a "phlogistic process," dephlogisticated air took it up and removed it by exhalation. T h e change in color of the blood passing through the lungs was due to loss of phlogiston. According to Priestley, "One great use of the blood must be to discharge the phlogiston with which the animal system abounds, imbibing it in the course of its circulation and imparting it to the air with which it is brought in contact, in the lungs." 9 T h e days of the phlogiston theory were numbered, however, and Priestley was almost its last defender. His own discovery of oxygen led Antoine Laurent Lavoisier (1745-1794) to accomplish the overthrown of the phlogiston theory and to bring about a proper realization of the function of oxygen in chemistry. T h e

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story of Lavoisier's gradual recognition of the mechanism of oxidation, discarding of phlogiston, revision of the chemical nomenclature, and of the gradual but decisive acceptance of the new chemistry has often been told. Here we are concerned with the significance of these steps in the establishment of modern biochemical concepts. The first important study made by Lavoisier after he learned of Priestley's discovery of oxygen was presented in 1775. Lavoisier heated mercuric oxide with charcoal and obtained mercury and fixed air. He then heated the oxide alone and obtained oxygen. Thus fixed air was a compound of carbon and oxygen. As early as 1777 Lavoisier also began studies of animal respiration. He allowed a sparrow to breathe common air. After the death of the bird the fixed air which had formed was absorbed with caustic alkali (which became mild, proving that fixed air had actually been given off). The residual air was identical with that produced when mercury was calcined in ordinary air. Addition of onefourth its volume of "eminently respirable air,"as Lavoisier then called oxygen, regenerated the original air. 10 He showed that the residual "mephitic air" (nitrogen) was a purely passive medium which entered and left the lungs unchanged. In the same year, Adair Crawford (1748-1795) carried out the first direct experiments on animal heat, which he published in 1779. Crawford had visited Black, and he knew the theory of specific heat which Black was expounding in his lectures. Based on this theory Crawford devised a calorimeter in which he could measure the heat output of animals. From his experiments he concluded: "The quantity of air phlogisticated by a man in a minute is found by experiment to be equal to that which is phlogisticated by a candle in the same space of time. And hence a man is continually deriving as much heat from the air as is produced by the burning of a candle." 11 Crawford called the quantity of heat in a body the "absolute heat." He believed that the atmosphere contained more absolute heat than did the air expired in the lungs. Blood passing from the lungs to the heart contained more absolute heat than that passing from the heart to the lungs. Therefore animal heat was produced in the lungs by Priestley's "phlogistic process" and was given off gradually to

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the body as the blood circulated. This conclusion was criticized by Lagrange, who said that if the theory were true, the lungs would be consumed. 12 However, this idea of combustion in the lungs was accepted by Lavoisier in his famous paper on combustion in general, presented to the Academy of Sciences in 1777 and published in 1780,13 in which he said "Pure air passing through the lungs suffers a decomposition analogous to that which takes place in the combustion of charcoal. Now in the combustion of the latter, matter of fire is set free. Therefore in the lungs there must be in the interval between inspiration and expiration a similar liberation of matter of fire, and it is doubtless this, which, carried by the blood throughout the animal economy, maintains there a constant heat of about 32 λ/ι Reaumur. This idea . . . rests on two constant and incontrovertible facts, namely: on the decomposition of pure air in the lung and on the liberation of the matter of heat which always accompanies the decomposition of pure air, that is, every change of pure air to fixed air." In this passage can be seen the major error of Lavoisier, his inability entirely to get rid of a phlogistic residue, the matter of fire. He later called this caloric and it remained a part of scientific thinking for many years. Lavoisier himself believed that gaseous oxygen was a compound of oxygen principle and caloric, and when oxidation occurred, caloric (heat) was liberated while the oxygen principle combined with the material undergoing combustion. A second major difficulty which Lavoisier faced at this time was also noted in his paper. Pure air had to react with something to produce fixed air, and he did not then see just what the combustible material was. In 1781 he decided to call fixed air "carbonic acid" and he was then ready to seek its source. 14 In 1783 Lavoisier in association with the famous mathematician Pierre Simon Laplace (1749-1827) described the invention of an ice calorimeter with which the two men carried out many studies on heat and laid the foundations for the science of thermochemistry. T h e major conclusion from their work was that as much heat is absorbed in the decomposition of a chemical compound as is evolved in its formation. 15 Applying their results to respiration, they calculated from the amount of carbon dioxide produced by

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a guinea pig in a given time how much heat should have been liberated in the formation of this amount of gas, and they felt that their calculations agreed well with the heat produced by the animal as measured directly for this time interval in their calorimeter. The Lavoisier-Laplace theory of respiration was expressed as follows: "Respiration is thus a combustion, very slow, it is true, but perfectly similar to that of carbon; it occurs in the interior of the lungs, without disengagement of visible light since the matter of fire which becomes free is at once absorbed by the humidity of these organs. The heat developed in this combustion communicates itself to the blood which traverses the lungs and from there it spreads over all the animal system." 16 This theory is very similar to that of Crawford, but it was based on much sounder evidence. Between 1792 and 1799 experiments by Spallanzani and Vauquelin showed that the phenomenon of animal heat was general, since worms, grasshoppers, and snails also took up oxygen, gave off carbon dioxide, and evolved heat. It was observed that the greater heat of warm-blooded animals was related to greater absorption of oxygen. In 1785, after the composition of water had been established by Cavendish, Lavoisier recognized that some of the oxygen taken into the body was used to form water. He now felt that the substance which combined with the oxygen in the lungs was some sort of carbonaceous matter. In 1790 he called it "carbonized hydrogen," by which he apparently meant a hydrocarbon radical. 17 In 1785 he began a series of experiments with Armand Seguin (1765-1835) to measure the amount of oxygen absorbed by animals and man under various conditions. They reported in 17891790 that more oxygen was absorbed when the temperature outside the body was low, when food was being digested, and especially when physical work was being performed. 1 8 Lavoisier noted, "This kind of observation suggests a comparison of forces concerning which no other report exists. One can learn, for example, how many pounds of weight lifting correspond to the efforts of one who reads aloud or of a musician who plays a musical instrument. One might even value in mechanistic terms the work of a philosopher who thinks, the man of letters who writes, the musician who composes. These factors, which have been considered

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purely moral, have something of the physical and material which this report allows us to compare with the activities of the man who labors with his hands." 19 It is worth noting that just such measurements were made toward the end of the nineteenth century. Lavoisier and Seguin were carrying out these experiments as the French Revolution was growing more violent, and Lavoisier himself was probably too occupied with governmental affairs to put all his ideas in final form. Apparently, however, he was beginning to wonder whether the lungs were really the only source of heat production, for he noted "there is no decisive proof that it [carbonic acid] is formed immediately in the lung or in the course of the circulation . . . it is possible that part . . . is formed by digestion, that it is introduced into the circulation with the chyle, and at last, reaching the lung, it is disengaged from the blood in proportion as the oxygen combines with it by a superior affinity." 20 At any rate, Lavoisier's physiological studies were ended by his arrest and execution in 1794. Another major biological advance at the end of the eighteenth century also stemmed from the progress of pneumatic chemistry. This was the recognition of photosynthesis. T h e work was begun by Priestley as the result of a theory of the Irish physician David Macbride (1726-1778), who believed that bodies were held together by the fixed air they contained. Putrefaction of meat occurred when this air escaped, and Macbride therefore tried to prevent this by immersing the meat in an atmosphere of the gas. It was this theory which suggested to Priestley the attempt to grow plants in pure carbon dioxide. 21 In 1771 he had observed that a sprig of mint growing in water gave off an air in which candles could burn. He then put the mint in a vessel containing air in which a candle had been extinguished. Ten days later a candle once more burned in this air. After a long interruption he resumed this study in 1777 and then found that not only mint but also the "green matter" which deposited on the walls of his vessels gave off bubbles of pure dephlogisticated air. He was not sure that the green matter was of plant origin, and so missed the essential fact of photosynthesis. T h e role of plants in photosynthesis was discovered by Jan

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Ingen-Housz (1738-1799), a Dutch physician who achieved a successful careeer in Vienna and came to England in 1779. Beginning in J u n e of that year he carried out over 500 experiments in three months and in October rushed his results into print. 22 Because of his haste he made a number of mistakes, but he recognized the essential facts that the phenomenon he was studying was caused by plants, that light was required for the production of the gas, that its production was proportional to the intensity of the light, that only the green parts of the plants produced the gas, and that at night only noxious air was given o f f by the plants. Priestley, working more slowly and carefully, came to the same conclusions at the about the same time, but he was forestalled in claiming priority by the haste with which Ingen-Housz published. 23 Similar experiments were being carried out at this time in Geneva by J e a n Senebier (1742-1809), who in 1782 went beyond Ingen-Housz by recognizing that it was "fixed air dissolved in water which is the nourishment which plants draw from the air which bathes them and the source of the pure air which they furnish by the elaboration to which they make it submit." IngenHousz denied the necessity of fixed air, and he and Senebier engaged in a long polemic in their writings. 24 Lavoisier entered the picture in 1786 when he proposed a mechanism for photosynthesis. He suggested that, since oxidation converts vegetable matter into carbonic acid and water, the reverse reaction must occur in plants. Carbonic acid and water would combine to form oils and resins, which he believed to be low in oxygen. T h e extra oxygen was threfore released as a gas. 2 5 In 1796 Ingen-Housz accepted Lavoisier's theories and explained the photosynthetic process in terms of carbonic acid and oxygen, noting that plants receive their carbon from carbonic acid. He believed that this gas was obtained from the air and not from the soil, as Senebier tended to think. This fact was proved by the studies of Nicolas Theodore de Saussure (1767-1845), who showed by quantitative experiments in 18 0 4 2 6 that the carbon dioxide came from the atmosphere, that all the carbon in plants came from this gas, and for the first time recognized that the

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other substance essential for photosynthesis was water. 27 He showed that the mineral constituents of plants come from the soil on which they grown. 28 T h e carbon cycle, which had been envisaged in reverse by Stahl, could now be understood, and the role of plants as the primary source of animal life could be fully realized.

12 Animal Chemistry

T h e growing importance of the chemical approach of biological problems at the end of the eighteenth century was in large part due to the increased emphasis on the quantitative aspects of chemistry. This change was the result of a specific recognition of ideas that had been gradually developing for many years. Probably the chief of these was the concept of the conservation of matter, which had been accepted implicitly even in work dating from the seventeenth century. For example, Angelo Sala (15761637) had prepared copper sulfate in 1617 by treating a weighed amount of copper with sulfuric acid and then decomposing the salt, recovering the original amount of copper. 1 As methods for quantitative analysis of inorganic compounds developed, the concept was extended, again implicitly. Many eighteenth-century chemists were also sure that chemical compounds had a fixed and definite composition. 2 Utilization of this concept of constant composition increased as the growing interest in mineralogy led to the discovery of more and more minerals. As a result of these developments Lavoisier, who relied com-

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pletely on both concepts, was led to write the first chemical equation: must [juice] of grapes = carbonic acid + alcohol and to say, "We may consider the substances submitted to fermentation, and the products resulting from that operation, as forming an algebraic equation, and, by successively supposing each of the elements in this equation unknown, we can calculate their values in succession and thus verify our experiments by calculation and our calculations by experiment reciprocally." 3 In the biological field experimental difficulties were greater than in the inorganic, but chemists tended to feel that the same law should apply in both. Major progress was made when it was recognized that the standard method for "analysis" of animal and vegetable meterials, dry distillation, was unsatisfactory because much the same substances were obtained from everything studied. This analytical method had led chemists to the concept of five elements: spirit, phlegm, oil, salt, and earth the products of the distillation, but these were not individually characterized substances. 4 Chemists realized that, as in the case of minerals, a variety of different reactions had to be employed to determine the actual composition of the substances which made up living organisms. Over a long period of time the use of solvent extraction for the separation of chemical substances from plant materials gradually replaced the methods of distillation which had prevailed from Alexandrian times. 5 As an illustration of the application of chemical ideas, even by physicians, to a problem which had been of great physiological interest, the change in attitude toward fibers may be considered. Haller, for all his emphasis on the importance of these structures, could say only that they were formed from the union of earth, water, oil, iron, and air, but he had no idea of how this union occurred. In 1795 Johann Christian Reil (1759-1813) could propose a mechanism for their formation. He believed they grew by a process of crystallization analogous to that which occurred in the inorganic world. He said: "Animal crystallization differs for different organs." T h e material to be added was applied to the organic unit just as salt in solution was applied to the surface of

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a cuboidal crystal of salt. Just as the "seed" of a salt crystal drew what it needed from the surrounding fluid, so the organic units attracted what they needed in accord with the rules which controlled them. 6 T h e growing systematization of organic analysis was well illustrated by the analytical methods used by Antoine Francois de Fourcroy (1755-1809) in studying a sample of cinchona bark from Santo Domingo. Extracts of the bark were made by successive treatments, first with water and then with alcohol. The substances obtained by evaporation of the extracts were further studied for solubility in alcohol and for their reactions with various acids and alkalis.7 Another example of progress in the study of individual chemicals was Fourcroy's isolation at about the same time of specific substances from gallstones. He characterized these by their melting points and solubilities in alcohol, which showed him that he was dealing with chemical individuals. 8 Guerlac has pointed out that it was not until this period that chemical textbooks began to describe compounds in terms of physical constants and measurable chemical properties. 9 In large part because of these changes in laboratory techniques for handling and identifying compounds of biological importance, chemists began to isolate increasing numbers of such compounds from living organisms. Stimulated by their success with complex mixtures of minerals, they began to study animal and vegetable tissues and fluids from the standpoint of their individual constituents. This was the chemical rather than the physiological approach. The brilliant Swedish chemist, Scheele, in addition to his discovery of oxygen and numerous minerals, developed a method for isolating organic acids through their calcium salts which permitted him to obtain substances such as tartaric, citric, malic, and lactic acids. He isolated uric acid from urinary calculi. By distillation of potassium ferrocyanide he obtained hydrocyanic acid (whose taste he described). By heating oils with litharge he prepared a "sweet" principle of oils and fats," that is, glycerol. 10 Johann Gottlieb Gahn (1745-1818), in a study carried out in 1769 and reported by Scheele, showed that bone consisted of cal-

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d u m phosphate. 11 Charles Hatchett (1765-1847) tested teeth and in 1799 showed that enamel was also composed of calcium phosphate and not the carbonate, as had been proposed. 12 Quantitative analysis of the teeth by Pepys followed in 1803. 13 The presence of fluorine in teeth was shown by Domenico Morichini in 1805, and for many years there was a controversy as to the presence or absence of this element in bones and teeth. 14 The difficulty arose because of the variability of the quantity of fluorine in the diet and hence its variable deposition in calcified tissues. In 1807 Fourcroy and his friend and collaborator Nicolas Louis Vauquelin (1763-1829) found phosphorus combined directly with carbon in the roe of carp. This was the first discovery of organically bound phosphorus. Previously it had always been associated with inorganic elements, as in bones and teeth. 15 Hillaire Martin Rouelle (1718-1779) studied milk sugar, starch, and gluten ("a glutenous material which I also call vegetoanimal"). Independently of Boerhaave he isolated urea from urine. Later he was often credited with priority in its discovery. 16 While these studies of biological compounds were going on, methods for their analysis were also being developed. This could not have been done before the gaseous elements were found, but once these were known, methods for their quantitative determination were worked out. Between 1780 and 1786 Claude Louis Berthollet (1748-1822) discovered that nitrogen is present in most animal substances. 17 In 1785 he found that ammonia was a compound of hydrogen and nitrogen. 18 It now became possible to replace the older vague idea that animal substances contained "uriniferous salts" (ammonia compounds) by the more precise recognition that nitrogen entered into their composition. At about the same time Lavoisier developed the first reasonably satisfactory method for determining carbon, hydrogen, and oxygen. In 1787 he burned substances such as wax or alcohol (mixed with oli've oil to reduce danger of explosions) with oxygen in a large bell jar and weighed the amount of carbon dioxide absorbed by caustic potash in the jar. Water was determined by difference. He did not allow for oxygen in the organic compound, assuming that it was all present as water, and so his quantitative results were not

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very significant, but his method was a precursor of those which would make it possible to determine the true composition of physiologically important compounds. 19 Although really satisfactory methods of organic analysis had to await the development of the Liebig procedure, enough was known at the beginning of the nineteenth century for chemists to begin to form a picture of the reactions that went on in the body. Fourcroy and others believed that most inorganic substances were composed of only two elements, that is, were binary compounds. Starches, sugars, and fats were oxides of hydrocarbon radicals (a favorite idea of Lavoisier) and so were ternary substances. Gluten, albumin, and fibrin also contained nitrogen and so were quaternary compounds. 2 0 Reactions in the body consisted either in adding or removing elements or in rearranging those already present. 21 T h e distinction between animal and vegetable substances was now explained by the lack of nitrogen in the latter. This raised a problem for Fourcroy, who neglected the early work on gluten in flour and could not understand how herbivorous animals obtained their nitrogen. At first he thought it might be absorbed through their lungs as a gas. However, in 1789 he was able to precipitate an albuminous substance from plant juices, and once more to isolate gluten from wheat flour. He could then explain the source of nitrogen in plant-eating animals. 22 T h e three animal nitrogenous compounds then known, fibrin, albumin, and gelatin, were considered to be interconvertible by addition or subtraction of small amounts of one or more of their elements. 23 A theory of nutrition which became popular at the end of the eighteenth century was that proposed by the French physician Jean Noel Halle' (1754-1822) in 1791.24 He adopted the terminology of Boerhaave and Haller in explaining his new theory of animalization. 25 He defined animalization as the change of vegetable into animal substances, and assimilation as the passage of nutrients into a state which made them resemble the parts of which the body is composed. He thought that all animal and vegetable substances could be converted to oxalic acid by treatment with nitric acid, and thus all had the same base. Addition of carbon or nitrogen to this base converted it to a specific nutritive

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substance. Acescent materials f r o m plants h a d had m u c h carbon a n d little nitrogen a d d e d , while alkalescent animal substances were d o m i n a t e d by nitrogen. D u r i n g animalization, the c o m m o n base combined with nitrogen a n d lost carbon. T h e process took place progressively, first in the intestines, t h e n in t h e lungs, a n d finally some changes occurred in the skin. T h e theory h a d some a d h e r e n t s even as late as 1830. A p r o m i n e n t physiologist, A n t h e l m R i c h e r a n d , t h o u g h t that d u r i n g animalization n u t r i e n t s c h a n g e d successively f r o m gelatin to albumin, a n d t h e n to fibrin. Blood fibrin solidified to muscle fibers.26 F r o m the work described above, a n d f r o m t h e isolated observations of new substances derived f r o m living organisms m a d e by many chemists, a new b r a n c h of science, "animal chemistry," was growing u p , b u t it was still in a very e l e m e n t a r y stage of developm e n t . T h e m a n w h o ultimately became almost the final authority on chemical matters of his day, J o n s J a c o b Berzelius (1770-1848), became interested in this subject early in his career. In 1810 he gave an a d d r e s s which was published as A View of the Progress and Present State of Animal Chemistry. T h i s effectively s u m m a r i z e d t h e condition of the science at t h e b e g i n n i n g of t h e n i n e t e e n t h century. 2 7 H e b e g a n by stating that it was a n " i n f a n t science" which could not have existed b e f o r e the work of Scheele, Black, Priestley, a n d Lavoisier. 2 8 However, h e was not very optimistic, so f a r as f u t u r e progress went, since "the cause of most of the p h e n o m e n a within t h e animal body lies so deeply h i d d e n f r o m o u r view that it certainly never will be f o u n d . We call this h i d d e n cause vital power a n d like m a n y o t h e r s w h o b e f o r e us have in vain directed their d e l u d e d attention on this point, we m a k e use of a word to which we can affix n o idea." 2 9 T h i s view was justified, h e felt, because "the brain a n d nerves d e t e r m i n e altogether t h e chemical processes which occur in the body" converting t h e blood into o t h e r b o d y fluids and tissues. Chemistry could n o t show how the nervous system worked. 3 0 T h i s pessimistic note in relation to chemistry r u n s t h r o u g h the entire book. Berzelius reviewed t h e work of m a n y investigators a n d n o t e d t h e various c o m p o u n d s which they f o u n d in d i f f e r e n t parts of the body, but h e confessed that h e did n o t know what these c o m p o u n d s accomplished. H e knew that iron was n o t pres-

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ent in the body as a salt, but he did not know how it was combined, to what the color of the blood was due, nor how the blood coagulates. 31 He said that our understanding of digestion stops short when the nervous system begins to determine the chemical state of the process. 32 Gastric juice could dissolve food, but the reason was not known. 33 He summed up his knowledge of digestion: "the alimentary matters are accurately triturated in the mouth, received into the stomach, and there converted by the gastric juice into a uniform fluid, which is precipitated in the duodenum by the bile. T h e solution is filtered in the intestines by means of the absorbents, and the precipitated mattter is washed by the the intestinal fluid, which is again absorbed, in the same manner as precipitates are edulcorated in our common filtering apparatus, after which the washed matter is evacuated." 34 It is of interest that he mentions that he himself had observed the presence of "alkaline lactate of potash" in blood. 35 He had found this in 1808 in the blood of stags who had been hunted and thus had been expending much energy. 36 In spite of his apparent hopelessness as to real progress in animal chemistry, Berzelius did feel that he had found a new approach to the subject which might bring better results than had yet been obtained. He concluded his address as follows: "Finally with regard to the manner in which I have endeavoured to treat the subject of Animal Chemistry, it has been altogether different from that of my predecessors, who, considering it as part of general chemical knowledge, have all divided the productions of the animal body into certain classes, and described them only as objects of analytical chemistry, to which they have added an appendix, with some general reflections on the economy of animal life. But this mode of treating Animal Chemistry is altogether without an object, and gives the results of chemical investigations little more than technical value, which, however, is entirely foreign to Animal Chemistry, properly so called. For my part, I have endeavoured to unite chemical and anatomical researches in the pursuit of one common object, in order to give to the investigation of the Animal Chemist, a determined and scientific tendency, and to his efforts, a physiological view. As my predecessors have not always begun from the same point, or taken their aim

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in the same direction, it has happened that much has been overlooked by them which might have been found without difficulty, and thereby I have been enabled, in the experiments which I have had an opportunity of institution, to discover or prove many circumstances, till then unknown or imperfectly stated." 37 The increasing emphasis on synthesizing isolated facts into a system indicated in this passage from Berzelius soon produced promising results. In the early years of the nineteenth century the classification of nutrient materials became more precise. It was generally accepted that nitrogen was the characteristic element of animal tissues, while vegetable substances contained little of this element. Therefore attention was centered on the sources and fate of nitrogen. There was an economic as well as a scientific motive in this interest. As Teich has pointed out, 38 there was a strong movement at the end of the eighteenth century, especially in England, to enclose land which had formerly been owned in common by the farmers of a given village. The resulting loss in farm lands resulted in a less adequate diet for laborers, and scientists were called upon to devise better diets. Obviously, feeding animal products could supply nitrogenous substances which did not have to be "animalized." Attempts were made to extract gelatin from bones as a nutritive supplement. 39 However, scientists realized that the best results would be obtained only when the behavior of nitrogen in the body was understood. The problem of elimination of nitrogen was solved by Fourcroy and Vauquelin in 1800. 40 They knew that any excess of the element would have to be removed from the body. When they discovered that urea contained more nitrogen than any other animal product, they realized that the element was removed by excretion of this compound. Since they assumed that urea was formed in the kidney, they felt that "the kidneys become for the physiologist the natural passage for nitrogen, as the lungs are for carbon, the liver for hydrogen. From blood arriving by the renal arteries the nitrogenous material separates, and thus the vital liquid, losing the superabundance of the principle, takes and conserves the equilibrium of composition which is necessary for it." T h e idea vaguely expressed here was developed into the concept of nitrogen balance by Liebig and others later in the century.

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The problem of the source of animal nitrogen was still troublesome. In spite of the opinions of Fourcroy, some scientists still believed that nitrogen might be taken in as a gas by the lungs. Obviously, only animal experiments could solve the question and determine whether the diet was the sole source of the element. An early and drastic experiment of this type was performed on himself by William Stark (1740-1770), who attempted to live for a prolonged period on bread and water. When symptoms of scurvy set in, he returned to a normal diet and recovered. However, he repeated the experiment with a diet of bread, flour, and honey, carried the test too far, and died. 41 The fact that all the nitrogen needed to support the animal body had to come from food was finally proved in 1816 by the French physiologist Francois Magendie (1783-1855). He wished to determine whether non-nitrogenous substances could support life. Accordingly, he fed dogs a diet composed entirely of sugar and distilled water. In the second week of this diet they began to fail. In the third week, Magendie observed what he called a "singular phenomenon," a severe ulceration of the eyes. Although he did not know it, Magendie was here describing the first reported case of xerophthalmia resulting from a lack of vitamin A in the diet, in addition to the protein deficiency. After a month on the diet the dogs died. Their bodies showed a total absence of fat, reduced muscle size, and an alkaline urine such as was found in herbivores. He concluded: "Sugar alone cannot nourish dogs." He repeated the experiment with diets composed only of olive oil or butter. Except that the eye condition did not occur, the results were identical. All the diets produced normal chyle in the stomach, so the results were not due to lack of digestion. Magendie concluded that the nitrogen in animals is in great part an extract of the food. 42 An improved method of organic analysis was developed by the chemists Joseph Louis Gay Lussac (1778-1850) and Louis-Jacques Thenard (1777-1857), 43 and as a result they were able to devise a classification of non-nitrogenous substances which distinguished between organic acids, fats, and sugars in terms of composition. Their "laws" stated in 184044 were as follows:

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1st Law. A vegetable substance is always acid whenever in this substance oxygen is to hydrogen in a relation greater than in water. 2nd Law. A vegetable substance is always oily or resinous or alcoholic, etc. whenever in this substance oxygen is to hydrogen in a relation smaller than in water. 3rd Law. Finally a vegetable substance is neither acid nor resinous and is analogous to sugar, to gum [as dextrin was then called], to starch, to milk sugar, to wood fiber, to the crystalline principle of manna whenever in the substance oxygen is to hydrogen in the same relation as in water. Thus in supposing for an instant that hydrogen and oxygen were in the state of water in the vegetable substance, which we are far from regarding as true, vegetable acids would be formed of carbon, of water, and oxygen in varying proportions. Resins, fixed and volatile oils, alchohol, and ether would be of carbon, water, and hydrogen, also in varying proportions. Finally, sugar, gum, starch, milk sugar, wood fibers, crystalline principle of manna would only be formed of carbon and water, and would differ only by the larger or smaller quantity which they contain. Between 1813 and 1823, when his results were published in book form, Michel Eugene Chevreul (1786-1889) determined the composition of the natural fats. 45 He studied the saponification process in detail, isolating from the reaction the salts, which yielded a number of fatty acids from butyric to stearic. These he characterized by melting points. He discovered their relation to glycerol, which he also recovered. He discussed different hypotheses as to the constitution of the fats, but the one which seemed most probable to him was that they were formed immediately from fatty acids and a compound which formed glycerol by fixing water. Thus the fats were the first of the major nutrients whose essential chemical nature became known. Chemical analysis had now differentiated the three classes of food materials, and a formal classification could be made. This was done in 1827 by the "English physician William Prout (17851850). He classified foodstuffs into the saccharine, the oily, and the albuminous groups. He tried to analyze the saccharine sub-

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stances, which he called "vegetable aliments." 46 This classification was easily accepted and has remained f u n d a m e n t a l ever since, though the names were changed. T h e term "protein", suggested by Berzelius, was adopted after 1838, when it was publicized by Mulder, 4 7 and the n a m e carbohydrate {Kohlenhydrat) was proposed by Schmidt in 1844. 48

13 Nineteenth-Century Vitalism

T h e term vitalism can be applied in one f o r m or another to the thinking of the majority of the scientists concerned with any biological subject d u r i n g most of the nineteenth century. However, this does not m e a n that all held the same theory. Rather it signifies that sooner or later each scientist reached a level of speculation as to the mechanisms of the living organism at which he could no longer explain these mechanisms with the facts at his disposal. T h e point at which this level was reached differed in individual cases, but the fact seemingly could not be denied that there was a distinction between the inorganic and the organic worlds; the unorganized and the organized as the distinction was often expressed. After the popularization of the idea of a vital force by Barthez the term came to cover a multitude of concepts. T o some it represented an actual substance characteristic of life, to others it was a force which operated on the inorganic elements to give them unique properties when it acted. Probably the best statement of the general situation was the remark of Berzelius: "We make use of a word to which we can affix no idea." T h e differing approach of the physiologist and the chemist to their sciences, already mentioned, was also shown in their idea

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of vitalism. A distinction in these terms has been made by Jorgenson, 1 who defined "physiological vitalism" as that which denies that life can generate itself, but which holds that once generated by creation or multiplication, life follows natural laws. "Chemical vitalism" asserts the existence of a chemical affinity which is directed against the usual inorganic affinities. Lipman 2 points out that this distinction is too restrictive and says, as does Mendelsohn, 3 that an individual may hold both these views. Nevertheless there is a real difference between the physiological and the chemical views. T h e physiologists who were termed vitalists insisted chiefly on the impossibility of spontaneous or laboratory creation of life or even of the physiological fluids characteristic of life. Chemists were less concerned about this point. They were mainly interested in the reactions of the compounds they studied, whether these were prepared by the chemist in his laboratory or were isolated from body tissues or fluids, but they wondered about the possible interference of a vital force with their chemical reactions. T h e vitalist-mechanist controversy was not as intense among chemists as among physiologists, yet it had biochemical overtones for both and led to investigations which eventually tended to reconcile the views of both groups. T he theory of a vital force arose among physiologists before it reached the chemists, chiefly because, until chemistry had developed its more or less independent identity, all speculations as to bodily mechanisms had to be based on physiological experiments. Not enough was known of the reactions of chemical compounds to permit theories as to how such reactions could occur. T h e vital processes which occurred were held to take place in body fluids, tissues, and organs. Even among physiologists, however, there was a wide variety of ideas, ranging from almost mystical concepts to theories which came close to being chemical. An example of the type of argument used by the exponents of extreme physiological vitalism has been quoted by Klickstein.4 Α vitalist and a "chemicalist" are arguing. "The vitalist, lifting a small covered dish, removed the lid, and presenting it to his opponent, said: here, Sir, is a small quantity of well-prepared beef, potatoes, and gravy—will you oblige me by taking it into your laboratory, and changing it into genuine chyme? With an air of

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embarrassment, the chemicalist replied—really, Sir, I cannot, otherwise than by eating it. That I can do myself, returned the challenger and a pig can do the same as well as us." As early as 1795 J. C. Reil believed that vital force indicated the relation of several individual phenomena to a special kind of matter found only in living nature. His theory of crystallization of fibers already mentioned was an example. He thought that eventually chemistry would explain these phenomena and the idea of a vital force could be discarded. 5 T h e most influential French physiologists of the early nineteenth century belonged to a group which Temkin called vitalistic materialists. 6 They worked largely on living animals and tried to base all their conclusions as far as possible on physical laws. Yet they still felt that some sort of vital force of a special kind lay behind their observed and postulated mechanisms. Xavier Bichat (1771-1802) felt that the special vital powers resided in individual tissues and organs. 7 Francois Magendie moved in the direction of physical explanation of body mechanics but relied in some cases on vital phenomena as explanations. His ideas were carried further by his famous student, Claude Bernard (1813-1878), who said, "Life cannot be characterized exclusively by either a vitalist or a mechanist conception." 8 In Germany the most influential physiologist of the early part of the century was Johannes Müller (1801-1858), founder of a school in which many important scientists were trained. He was well acquainted with the chemistry of his day, and at the same time was a confirmed vitalist. He stressed the distinction between binary inorganic compounds and the more complex organic ones. For formation of the latter an organizing force was required. He denied that the findings of inorganic chemistry could be used to explain the chemistry of organisms. 9 In Germany, however, his students were probably repelled by the excesses of the fantastic school of Naturphilosophie. Adherents of this school, led by F. W. A. Schelling (1775-1854), believed in the unity of nature, expressed in a World Spirit. All matter possessed this spirit, but organized bodies showed it most actively. It could be appreciated intuitively, and Schelling was opposed to empirical science. 10 It was in part due to a revulsion from such

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views that the students of the vitalist Müller and their associates, especially Du Bois-Reymond, Ludwig, Helmholtz, and Brücke, whom Temkin calls mechanistic materialists, wished to "dissolve physiology into biochemistry and biophysics." 11 A typical physiological approach to the problem of vitalism occurred with the development of the cell theory. In 1835 Felix Dujardin (1801-1860), a protozoologist, had given the name "sarcode" to the gelatinous fluid which appeared to make up the substance of living, organized rhizopods. 12 In 1838 Mathias Jacob Schleiden (1804-1881) and in 1839 Theodor Schwann (18101882) suggested that cells form the basic structure of all living tissues. T h e botanist Hugo von Mohl (1805-1872) described plant cells in detail and stressed the fluid content of the cell as the significant feature of life rather than the cell walls, which Schwann had considered basic. In 1846 von Mohl proposed the name "protoplasm" for this fluid in plant cells (although Purkinje had previously used the term in a somewhat different sense 13 ). In 1850 Ferdinand Cohn (1828-1898) pointed out the identity of plant and animal protoplasms. During the next twenty years protoplasm assumed a central place in the thinking of many biologists as the essential bearer of the phenomena of life. In 1868 Thomas Henry Huxley (1825-1895) delivered a lecture in which he called protoplasm "the physical basis of life." 14 He stressed the fact that all life resided in the homogeneous, protinaceous substance, protoplasm. He felt that "by the advance of molecular physics" all the properties of life would be referred to the chemical and physical properties of the molecules which made up this substance. 15 Although Huxley denied that he was solely a materialist, his position was interpreted by the vitalists as materialistic, and, as with so many of Huxley's popularizations of scientific ideas, this led to a violent controversy. While most physiologists took a position between the extreme enthusiasm of Huxley for a materialistic protoplasm and the views of convinced vitalists, the general feeling among them favored a mild form of vitalism. It was not until the end of the century that chemical and physiological views could be brought together and vitalism would gradually disappear. 16 While the physiologists in their discussion of protoplasm usually made at least some mention of its chemical composition, it is clear

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that they were really thinking of it as a single substance, just as they had earlier thought of the various body fluids as unit materials whose distinctive properties were not referred back to individual constituents. T h e tendency of chemists to think in terms of such constituents was reflected in their ideas of vitalism, and thus, as indicated, chemical vitalism differed from physiological vitalism. Berzelius, the most influential chemist of his day, had said in 1810 that a "vital force," probably residing in the nervous system, was responsible for all bodily processes, and he did not believe that this power would ever be understood. During the next decade he developed his dualistic system. According to this, all compounds consisted of two parts, an acid oxide and a basic oxide, held together by electrochemical forces. He thought that inorganic compounds consisted of simple radicals held together in this way, while organic compounds were composed of complex, that is, ternary or quaternary radicals. In the living body these were still held together by electrochemical forces according to the general laws of chemistry, but here the electrical forces were modified by the nerve force, which prevented the complex radical from breaking down to simple constituents. In 1818 he wrote, "Organic nature in living plant or animal bodies modifies the original electrochemical nature of the elements and binds them in entirely other ways and in other proportions than occurs in our chemical vessels."17 Thus this modifying force, his vital power, had a much more specific mechanism of action than was assigned in many of the vaguer pictures of the physiologists. When Berzelius published the first edition of his well-known textbook in 1827, he began it by writing: "In living nature the elements seem to obey entirely different laws than they do in the dead . . . This 'something' which we call vital force is situated entirely outside the inorganic elements and is not one of their original properties as are gravity, impenetrability, electrical polarity, and so on." These statements were repeated in later editions and only slightly modified in the last, incomplete edition of 1847. As Jorgensen says, this could only mean to his readers that Berzelius retained his vitalistic beliefs throughout his life, though he may have modified them somewhat in private. 18 Such a modification seems the more probable, since during the twenty years

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between the two editions a number of new ideas were developed and new discoveries made, often by Berzelius himself, which bore directly on his beliefs. It is true that in his last years he was bitterly fighting the chemical world in an attempt to justify theories which he had expressed in his younger years, and it is unlikely that he would have publicly changed any statement he had then made if he could avoid doing so. Nevertheless the new discoveries and ideas compelled some changes. In his 1827 edition Berzelius had said, "Art cannot combine the elements of inorganic nature in the manner of living nature. 19 In the next year his friend Friedrich Wöhler (1800-1882) found that when ammonia reacted with cyanic acid a product resulted which was not ammonium cyanate [(NH4NCO)] though it had the same empirical composition as that salt. Further study showed that it was urea [(NH2)2CO]. In the paper in which he reported this fact 20 Wöhler did not discuss the vitalistic implications of the laboratory formation of a compound hitherto known only from animal sources. In a letter to Berzelius he seemed to be somewhat more excited, stating that he could make urea without the need of an animal kidney. Berzelius replied that this was "important and beautiful," yet neither Wöhler nor Berzelius seemed to be greatly concerned about the significance for the vitalistic concept. Historians of science have held divided views on the effect of Wöhler's discovery on vitalistic thought. 2 1 It was known at the time that kidneys were not essential for urea formation, since Prevost and Dumas in 1823 had shown that the urea of blood was identical with that of urine, and that removal of the kidneys did not prevent formation of blood urea. They did not know the site of urea formation, but suspected that the liver was somehow involved. 22 This fact was not positively established until 1924. Nevertheless, urea was an animal product and it had now been formed in the laboratory. Early historians of chemistry claimed that vitalism had here suffered an overwhelming defeat. In 1944 McKie declared that the discovery had had almost no effect on vitalistic concepts, since the ammonium cyanate which was converted to urea had originally come from animal sources. 23 This explanation has not been generally accepted by other historians. They note that most of the vitalistic physiologists and chemists

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were chiefly concerned with minimizing the significance of the discovery rather than with discounting it altogether. Johannes Müller said that urea was not an animal product at all, since it was merely an excretion product. Charles Gerhardt (1816-1856) believed that "only the vital force operates to synthesize" and that by purely chemical forces water, carbon dioxide, and urea were formed as decomposition products which the chemist could not rebuild into the complex substances of animal tissues. The decomposition in the body was a kind of combustion. 24 Most chemists, however, were less concerned with the vitalistic significance of what was to them only another chemical reaction, but one of a type which was coming to be of great interest. In 1823 and 1824 Wöhler and Liebig had discovered that fulminic and cyanic acids had identical empirical compositions and yet were distinct substances. The new discovery of the same relationship between ammonium cyanate and urea was what apparently chiefly interested Berzelius. In 1832 he assembled all the information of phenomena of this type known to him and proposed the name isomer for compounds of this sort. 25 Thus his interest in the formation of urea was primarily because of its chemical significance, and he made no change in his comments on vital force in the 1837 edition of his textbook. T h e interest of most chemists, in fact, as Brooke has shown, was "how to ascertain the arrangement of elements within an organic compound, once its empirical formula was fixed."26 Berzelius also characterized another force which was to become important in the vitalist-mechanist controversy. In 1836 he drew together a large amount of experimental material, reports of which had been scattered through the literature. This included such reactions as the decomposition of starch to yield sugar in the presence of a small amount of acid (Kirchhoff, 1811) and the combination of oxygen and hydrogen in the presence of finely divided platinum (Döbereiner, 1822). In all his cases Berzelius felt that a new force was acting, and he proposed a name for it. "This new force, which was unknown until now, is common to organic and inorganic nature. I do not believe that it is a force entirely independent of the electrochemical affinities of matter; I believe, on the contrary, that it is only a new manifestation, but since we

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cannot see the connection and mutual dependence, it will be easier to designate it by a separate name. I will call this force catalytic force."27 T h e r e are obvious similarities here between catalytic and nerve force as Berzelius used the term, except that catalysis could also occur in the inorganic world. However, both in the title of his paper and in his application of the idea he was clearly thinking of catalysis in living organisms. H e said, "This force offers opportunities for n u m e r o u s applications in organic nature; thus it is only a r o u n d the eyes of potatoes that diastase is f o u n d ; it is by means of catalytic force of diastase that starch, which is insoluble, is t r a n s f o r m e d into sugar and gum, which, being soluble, f o r m the sap which appears in the germ of the potato. This very obvious example of the action of catalytic force in an organic secretion holds not only in the animal and vegetable kingdoms. It can, perhaps, be f o u n d , by following it up, that it is by an action analogous to catalytic force that there occurs secretion of very different bodies which are, however, all drawn f r o m one material: sap in plants a n d blood in animals." Jorgensen has suggested that when, in the 1847 edition of his textbook, Berzelius eliminated the term "vital force" and r e f e r r e d only to "something" he may have had catalytic force in mind mind. 2 8 In any case, the question of the synthesis of organic compounds was gradually settled as the century advanced. However significant Wöhler's preparation of urea may or may not have been, total synthesis of organic substances f r o m the elements was later achieved. In 1845 H e r m a n n Kolbe (1818-1884) r e p o r t e d the complete synthesis of acetic acid, 29 and in his book of 1860 Marcellin Berthelot (1827-1907) gave many examples of the synthesis of organic c o m p o u n d s f r o m the elements. 3 0 T h e discovery by Claude B e r n a r d in 1853 of formation of glycogen in the liver disproved the old idea that only plants could synthesize complex compounds, which were then eaten by animals. 3 1 This particular a r g u m e n t for vitalism could no longer be used in the vitalistmechanist controversy. Berzelius may have suspected that the vital force was electrical in nature, since it r e a r r a n g e d his electrochemically combined substances, but he did not specifically say so. Others were somewhat

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m o r e explicit in this respect. T h e English s u r g e o n J o h n Abernethy (1764-1831) claimed in 1817 that t h e r e was a principle of life, an actual substance of a n extremely subtle character, which was either electrical o r s o m e t h i n g very similar. This was o n e m o r e e x a m p l e of t h e idea of i m p o n d e r a b l e fluids which h a d so d o m i n a t e d scientific t h o u g h t in the eighteenth century a n d which was now reaching the e n d of its popularity. 3 2 T h e m u c h m o r e influential William P r o u t also believed in a vital a g e n t or agents which were n o t quite electricity a n d which resided in t h e nervous system. 3 3 T h e s e agents were the principles which exist in organized beings, 3 4 t h o u g h their intimate n a t u r e would probably always b e u n k n o w n . 3 5 T h e y were s u p e r i o r to t h e agents which act in the inorganic world—heat, light, a n d electricity—but they could n o t violate the basic laws of chemistry. T h e y could not create an e l e m e n t o r c h a n g e o n e into a n o t h e r , n o r could they combine a n e l e m e n t in a m a n n e r impossible f o r inorganic agents. H e expressly d e n i e d the "vague notion" of physiologists that organic agents could p r o d u c e results altogether d i f f e r e n t f r o m those that are p r o d u c e d u n d e r exactly similar conditions by inorganic agents. 3 6 A n organic a g e n t could, however, act o n a n individual molecule "to effect its ulterior p u r p o s e . " A hierarchy of h i g h e r a n d h i g h e r agents could a d a p t g r o u p s of molecules to such p u r p o s e s . H e was very clear that the living principles a r e not t h e result b u t t h e cause of organization. 3 7 I n his theory of t h e interaction of molecules h e was quite specific a n d suggested ideas which have their m o d e r n counterparts. H e recognized that organic bodies are built u p of the f o u r elements carbon, h y d r o g e n , oxygen, a n d nitrogen, which combine to give his t h r e e types of p r o x i m a t e substance: sugar, oil, a n d albumin. T h e d i f f e r e n c e s between individuals within these classes lay in the m i n u t e a m o u n t s of incidental ingredients they h a p p e n e d to contain. T h e s e included s u l f u r , p h o s p h o r u s , chlorine, fluorine, iron, potassium, sodium, calcium, m a g n e s i u m , " a n d probably m o r e besides." 3 8 T h e s e elements could exist in a state of s t r o n g repulsion f r o m each o t h e r a n d thus could modify t h e a r r a n g e m e n t of constituent molecules, a n d so alter the sensible p r o p e r t i e s of the substances p r o d u c e d by their combination. 3 9 A l t h o u g h the vital elements controlled these reactions, Prout h e r e

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presented a striking mechanism by which the results were achieved. Here was a case of a believer in a form of vitalism who yet could attempt to explain everything possible by, the facts of the chemistry he knew. An even more important scientist who combined the same tendencies was Justus Liebig (1803-1873). Liebig had been responsible for much of the early progress of organic chemistry. T h e studies he and Wöhler had carried out on benzoyl derivatives had established the radical theory which was a beginning of the understanding of chemical structure and which gave some insight into the mechanism of organic reactions. Therefore when he turned to argricultural and animal chemistry in the 1840's he was sure that chemical reactions would be found to account for much of what went on in the living organism. When he could explain a reaction by the behavior of molecules, he saw no need for the concept of a vital force. When he could not, he was not averse to assuming that such a force existed. Since in the majority of biochemical reactions of his day only the initial and final products were known and the intermediates which could show the mechanism were not, it is not surprising that he often had to revert to a vitalistic position. Thus he seemed sometimes a mechanist, sometimes a vitalist, and he was attacked by extremists of both factions as an example of the views they opposed. Actually, he views were quite consistent. 40 He objected to the idea of the participation of a living being in a chemical reaction, not to the idea of a vital force directing organic processes. This distinction has not always been appreciated. 41 T h e vital force, as he saw it, was as much a fact of nature as the force of gravity. It might not be possible to explain either force, but the effects of each could be observed and described. Vital force did not replace ordinary chemical forces, but it acted on their results to bring about new molecular rearrangements. This vitalistic explanation did not influence his study of life, but it served for an understanding of what he found. 4 2 Most of his writings could be read as purely chemical explanations of bodily reactions. This is why the extreme vitalist Charles Caldwell could attack him violently as follows: "for if there be in existence a more unscrupulous

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system of materialism than that contained in Liebig's Animal Chemistry, I know not where it is to be found. 4 3 After Liebig, the structural theory of organic chemistry made possible the synthesis of thousands of new compounds and an understanding of mechanisms of their reactions. Chemists no longer saw the need for a vital force. T h e German school of physiologists, Temkin's "mechanical materialists," discarded vitalism completely and turned to the rapidly advancing science of physics for an explanation of vital mechanisms. 44 For them man became "but a passing constellation of lifeless particles of matter". 45 It cannot be said that vitalism was completely extinguished. Even in the twentieth century Hans Driesch (1867-1941) continued to insist that the function of protoplasm could not be explained mechanically. However, with the accumulating mass of chemical and physiological information, vitalism did gradually disappear from biological thought.

14 Theories of Digestion and Assimilation in Mid-Nineteenth Century

By the early part of the nineteenth century animal chemistry had succeeded in identifying many of the important substances which are involved in body mechanisms and in making a beginning at classifying some of them. With this information available, it became possible to study more successfully the age-old problem of the digestion and assimilation of food. At this time the stomach was considered to be the most important organ for digestion. Too little was known of the action of the other digestive juices to permit much speculation as to their actions. T h e chief problem for investigation was thought to be the production of chyme, as the first product of reaction of foods with gastric juice was now called. The further problem of the change of chyme into chyle in the intestine was left for the future. T h e primary problem to be actively studied was the nature of the gastric juice. After Van Helmont, most workers had expressed serious doubts as to the presence of any acid in the stomach under normal conditions. However, this point was effectively cleared u p

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when Magendie in his influential textbook of 1817 reported an analysis of gastric juice by Chevreul. 1 According to this, it contained "much water, a very large quantity of mucus, the lactic acid of Berzelius united with an animal substance which is soluble in water and insoluble in alcohol, a little hydrochlorate [chloride] of ammonia, some hydrochlorate of potash, and a certain amount of hydrochlorate of soda." The acidity of the juice was thus established, but the ascription of the acidity to lactic acid remained a stumbling block for many years, even though definite evidence of the error of this view soon came from the work of William Prout. Prout is known in the history of chemistry chiefly for "Prout's Hypothesis," the idea which he presented anonymously in 18151816 that the atomic weights of all the elements are whole multiples of the atomic weights of hydrogen taken as unity. As has already been shown, his contributions to physiological chemistry were of very great importance. His desire to find unifying generalizations, apparent in his hypothesis, was also evident in his classification of foods into the three major groups (Chapter 12). A further illustration of his generalizing tendency was his attempt, even when he was a student, to account for the response of the organism to tactile feelings, tastes, smells, sounds, and colors. He believed that these sensations arose by contact of the nervous system with a single matter existing in five different forms: solid, liquid, gaseous, aetherial, and luciform. In the course of testing this theory he discovered the fact that the flavor of substances depended on a limited number of tastes combined with different odors. 2 In 1823 Prout made a report to the Royal Society of London 3 in which he described experiments on the extraction of the stomachs of various animals, killed after eating, with cold distilled water. 4 He found the extracts very acid but containing no sulfuric or phosphoric acids. He concluded: "The results then seem to demonstrate that free or at least unsaturated muriatic acid in no small quantity exists in the stomachs of these animals during the digestive process; and I have ascertained, in a general manner, that the same is the case in the stomachs of the hare, the horse, the calf, and the dog. I have also uniformly found free muriatic

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acid in great abundance in the acid fluid from the human stomach in severe cases of dyspepsia." In the comprehensive review of animal chemistry that he published in 1834, Prout considered the source of this acid. He believed the chlorine came from the common salt of the blood and that it separated from this salt and passed into the stomach as muriatic acid electrically. He asked himself what became of the soda and replied, "The soda remains behind, of course, in the blood, and a portion of it, no doubt, is required to preserve the weak alkaline condition essential to the fluidity of the blood" (a forecast of buffer action). T h e rest of the soda probably entered the bile and in the duodenum again combined with the acid separated from the blood by the stomach. The need for chlorine explained the craving of animals for salt.5 A long series of experiments on digestion of many types of food by many different species of animals was carried out in Heidelberg by Friedrich Tiedemann (1781-1861) and Leopold Gmelin (1788-1853) and was reported in 1826. They observed that when food was present in the stomach, the gastric juice was always acid, though the acidity varied under different conditions and corresponded to the digestibility of the foods. 6 They said, "It evidently follows from our experiments that digestion of aliments in the stomach consists of their solution by the gastric juice. Simple aliments such as albumin, fibrin, cheese, gelatin, vegetable mucus, starch, sugar, gluten, and the aliments composed of various constituent principles are dissolved by the juice." 7 According to their analyses the acidity was due to the presence of both hydrochloric and acetic acids, and in ruminants butyric acid was also present. 8 They admitted, however, that digestion might be due to something more than acids alone. 9 The nature of the acid would seem to have been settled by the experiments of the American physician William Beaumont (17851853), though in fact it was not. Beaumont had the opportunity to observe digestion directly in the human stomach. In 1822 he was called upon to treat the apparently fatal wound of a young Canadian woodsman, Alexis St. Martin, who had been accidently shot in the side. St. Martin recovered, but with a gastric fistula

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covered by a flap of skin. B e a u m o n t realized the u n i q u e o p p o r tunity of studying this case, a n d intermittently f o r t h e next ten years h e was able to m a k e direct studies of gastric juice a n d its effect o n various foods u n d e r d i f f e r i n g physiological conditions. His classic r e p o r t of his observations a p p e a r e d in 1833. 1 0 B e a u m o n t sent samples of gastric juice taken directly f r o m the stomach to Robley Dunglison (1796-1869) of the University of Virginia, who h a d followed his work closely and was well aware of the c u r r e n t theories of digestion, 1 1 a n d also the B e n j a m i n Sillim a n of Yale a n d to Berzelius. T h e sample to Berzelius took so long in r e a c h i n g him that the f a m o u s scientist did not believe his results to be significant, t h o u g h h e n o t e d t h e acidity. 12 Dunglison a n d Silliman a g r e e d t h e acid was hydrochloric. As an e x a m p l e of t h e progress of biochemical analysis since t h e time of Fourcroy, Dunglison's r e p o r t may b e q u o t e d : 'Since I last wrote you, my f r i e n d a n d colleague, Professor E m m e t t , a n d myself, have e x a m i n e d t h e bottle of gastric fluid which I b r o u g h t with m e f r o m Washington, a n d we have f o u n d it to contain f r e e Muriatic a n d Acetic acid, Phosphates a n d Muriates of Potassa, Soda, Magnesia a n d Lime, a n d an animal matter, soluble in cold water but insoluble in hot. W e w e r e satisfied, you recollect, in Washington, that f r e e muriatic acid was present, b u t I had n o conception it existed to the a m o u n t met with in o u r e x p e r i m e n t s h e r e . W e distilled t h e gastric fluid, w h e n the f r e e acid passed over, the salts a n d animal m a t t e r r e m a i n i n g in t h e retort. T h e quantity of chloride of silver t h r o w n d o w n o n t h e addition of nitrate of silver, was astonishing." 1 3 B e a u m o n t m a d e a c a r e f u l study of t h e effects of gastric juice o n f o o d s a n d concluded; "it is t h e most general solvent in n a t u r e of alimentary m a t t e r . . . It is capable even out of the stomach of e f f e c t i n g p e r f e c t digestion." 1 4 H e said, "We must, I think, r e g a r d this fluid as a chemical a g e n t a n d its o p e r a t i o n as a chemical action." 1 5 Like T i e d e m a n n a n d Gmelin h e n o t e d that "animal foods," fibrin, gelatin, a n d a l b u m i n were easily digested by gastric juice, especially w h e n they were finely divided, 1 6 t h o u g h h e failed to m a k e their observation that b u t t e r was not digested in t h e stomach. 1 7 T h e observations a n d e x p e r i m e n t s of B e a u m o n t w e r e soon k n o w n in E u r o p e , especially in G e r m a n y . In France in 1843

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Nicolas Blondlot (1810-1877), professor of chemistry at Nancy, prepared artificial gastric fistulas in animals and confirmed many of Beaumont's results. 18 In spite of all these studies, many chemists and physiologists refused to believe that hydrochloric acid was actually present in gastric juice. T h e claim of Magendie that the acid was lactic was accepted without much questioning by many scientists. Although Tiedemann and Gmelin had noted hydrochloric acid in the juice, they also reported the presence of acetic acid by which they said they meant only some organic acid. 19 An encyclopedic article of 1839 stated: "Dr. Prout indeed informs us, that a quantity of muriatic acid is always present in the stomach during digestion, but as there does not seem to be any decisive evidence of its appearance previously to the introduction of food into the stomach, we ought probably rather to consider it as developed by the process of digestion, than as entering into the constitution of the gastric juice, nor indeed, if it were so, are we able to explain the mode in which it operates in converting aliment into chyme." 20 In 1844 Claude Bernard and his friend Charles Barreswil (1817-1870), a chemist, said that they always found lactic acid with a little phosphoric acid in gastric juice. T h e phosphoric acid was probably the result of a secondary reaction of the lactic acid with the phosphates of the food. 21 In 1847 C. G. Lehmann of Leipzig believed that what little hydrochloric acid he found in the stomachs of fasting dogs came from the action of lactic acid on calcium chloride in the diet. 22 It is probable that in most of these cases the studies were made on fasting animals in which little gastric juice was present. Almost the final word on gastric acid came as the result of the careful researches of the Dorpat professors Friedrich Bidder (1810-1894) and Carl Schmidt (1822-1894). In their book of 1852 they said: "As a result of 18 concordant analyses we found that pure gastric juice from 18-20 hour fasting carnivores contained only free hydrochloric acid and no trace of lactic or other organic acids—the gastric juice of herbivores contained along with free hydrochloric acid a small quantity of lactic acid which however was derived from the nutrients rich in starch. The amount of this

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last acid was very variable, while that of the first seemed constant." 2 3 C l a u d e B e r n a r d was not convinced. P e r h a p s influenced by a d m i r a t i o n f o r his old teacher, Magendie, h e still believed the gastric acid was lactic. A l t h o u g h W a n g e n s t e e n has stated 2 4 that in his Leqons de physiologie experimentale appliquee ä la medecine of 1856 B e r n a r d "took pains to correct" his e r r o r , a r e a d i n g of t h e passage in question shows that h e was still d e f e n d i n g his earlier findings with Barreswil. 2 5 H e now a d m i t t e d that w h e n gastric juice was distilled, t h e lactic acid became sufficiently concentrated to liberate some hydrochloric acid f r o m t h e chlorides present, b u t h e concluded: " I n s u m m a r i z i n g these e x p e r i m e n t s we see that lactic acid a n d the acid of gastric juice show c o m m o n characteristics of being fixed on the fire, c a u g h t in distillation by water vapor, a n d changing hydrochloric acid f r o m chlorides. W e find in gastric juice all t h e characteristics of lactic acid. T h e existence of this acid a p p e a r s to us today to be beyond d o u b t . " T h e e x p e r i m e n t s h e quotes were all qualitative, a n d his interpretations were m a d e by analogy. T h e y could n o t stand against the quantitative analyses of B i d d e r and Schmidt, a n d t h e presence of hydrochloric acid as the gastric acid came to be accepted by most chemists a n d physiologists. Suspicion that s o m e t h i n g besides the acidity was involved in gastric digestion had existed f o r some time, a n d this fact was confirmed in 1836 by T h e o d o r Schwann. 2 6 Schwann was following a suggestion of 1834 by J . Eberle. H e , like others, h a d shown that gastric digestion could occur outside t h e stomach, a n d h e prep a r e d a digesting fluid by treating gastric mucosa with dilute hydrochloric acid. 2 7 Schwann showed that such t r e a t m e n t liberated a digestive principle f o r which h e p r o p o s e d t h e n a m e pepsin. H e said this principle must act by a catalytic or contact mechanism, since a small a m o u n t of it acted on a quantity of albumin. H e was thus applying immediately the Berzelius suggestion of a catalytic force. Liebig, who edited the j o u r n a l in which Schwann's p a p e r was published, was d o u b t f u l of its conclusions. I n a note at the e n d of t h e article h e w a r n e d that the word catalytic was only a n a m e a n d should not be used unless a n actual substance could be shown to exist by e l e m e n t a r y analysis. T h i s d e m a n d f o r an analysis n o d o u b t reflects t h e success Liebig h a d enjoyed in

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developing his method of organic analysis. In most of his work he relied strongly on analytical results. Actually, however, a similar catalytic agent had already been described and was one of the examples cited by Berzelius in his paper on the catalytic force. In 1833 Jean Francois Persoz (18051868) and Anselm Payen (1795-1871) had prepared an extract of malt which converted insoluble starch granules into soluble dextrin. 28 Since they believed the substance broke down an insoluble membrane on the surface of the starch granules and allowed a soluble material to escape, they called their extract diastase, from the Greek word for breaking. It was quickly realized, however, that here was an organic agent which catalyzed the same reaction with starch as that produced by dilute acids, as established by Kirchhof in 1811. It was also realized that saliva contained a similar principle, "animal diastase," since in 1831 Leuchs 29 had shown that this fluid also converted starch to sugar. The occurrence of a principle which acted thus on starch or dextrin was now shown to be an important agent in the digestive process. Mialhe in 1845 made a careful study of "salivary diastase" and showed that it was without action on fibrin, albumin, casein, gelatin, gluten, cane sugar, inulin, gum arabic, or woody material, but that it had an extraordinary effect on starch. It was precipitated by alcohol, but redissolved in water. 30 Pancreatic juice had been a puzzle for a long time, but methods for obtaining it were becoming more available. Bouchardat and Sandras found that this juice, or fragments of the pancreas, also liquefied starch and converted dextrin and glucose. 31 A similar observation was made by the Swiss physiologist G. G. Valentin (18 1 0-1883), 32 and the name abdominal salivary gland was suggested for the pancreas. Claude Bernard was much interested in the differences in digestion and assimilation between carnivorous and herbivorous animals. In the course of studies on dogs and rabbits he noted that the pancreatic juice entered in intestine at a point lower in the tract in rabbits than it did in dogs. It was only beyond this point that chyme was transformed into milky chyle. Following u p this fact, he made the major discovery that pancreatic juice contained a principle which split fats into fatty acids and glycerol,

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after which these products were absorbed. He published his first report on this in 184933 and issued a comprehensive monograph in 1856. 34 In this he not only showed the effects of pancreatic juice on starches and fats but indicated an effect also on proteins. The discovery of trypsin did not take place, however, until it was obtained by Bernard's student, Kühne, in 1876. It is amusing that when Bernard was made a Chevalier of the Legion of Honor for this work, the report contained a misprint to the effect that the award was made for "excellent work on the musical [instead of medical] properties of the pancreas." 35 Thus, by the middle of the nineteenth century the pathways of digestion and the functioning of the digestive juices were becoming fairly clear. An important fact which emerged from these studies was that a large number of chemical reactions in biological systems were catalyzed by certain active principles found in body fluids. T h e nature of these principles certainly was not known, but it was obvious that they played an important part in physiological processes. T h e old name "ferments" came to be applied specifically to such principles. As the understanding of the reactions in the digestive tract increased, it was natural that attention would be directed to a consideration of the further fate of substances after they had been absorbed. As long as the old idea of a sharp distinction between vegetable and animal kingdoms and their reactions dominated, little progress could be made. This idea, which had been stressed by Lavoisier, was emphasized in a lecture given by the prominent chemist Jean Baptiste Andre Dumas (1800-1884) in 1841, and this lecture was expanded in a book with the collaboration of Jean Baptiste Boussingault (1802-1887), Essai de statique chimique des etres organises. Here the distinction between plants and animals was very clearly stated, as the following table, taken from their book, shows. Animal A moving organism An oxidizing organism Exhales carbon dioxide, water, ammonia, nitrogen

Plant A non-moving organism A reducing organism Fixes carbon dioxide, water, ammonia, nitrogen

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Animal (cont.) Consumes oxygen, neutral nitrogenous compounds, fats, starches, sugars, gums Produces heat Produces electricity Restores its elements to the air or earth Transforms organic matter into inorganic

Plant (cont.) Produces oxygen, neutral nitrogenous compounds, fats, starches, sugars, gums Absorbs heat Absorbs electricity Draws its elements from the air or earth Transforms inorganic matter into organic 36

Dumas and Boussingault believed that fatty materials form only in plants and pass completely formed into animals. 37 These ideas were not sufficient for Claude Bernard. He felt that little could be learned of the processes of assimilation if the investigator knew only the substances absorbed and the products excreted. He compared this to knowing what went on in a house if he knew what went in at the door and what came out of the chimney. His aim was "to follow step by step and experimentally all the transformations of stubstances which the chemists were explaining experimentally." 38 For this purpose he designed an extensive program: to follow the fate of all types of foodstuffs in the body. His earliest studies had concerned the fate of the sugars, and so he began his work with these compounds. He found so much to do in this field that he never attacked the fate of the fats or proteins. 39 His work with sugars was facilitated by his association with Barreswil, who had devised a test for sugars with alkaline cupric salts stabilized by the presence of tartrates, the so-called blue liquid of Barreswil. It was essentially what later came to be called Fehling's solution. 40 Using this reagent, Bernard could easily detect the presence of sugar in various parts of the body. In his doctoral thesis of 1843 41 Bernard had reported that when cane sugar was injected directly into the blood, it was excreted unchanged, but when it was first treated with gastric juice, it did not appear in the urine. This convinced him that glucose was the only form of sugar used by the organism. The presence of sugar

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in the blood had by now been recognized, and a number of workers thought it originated in that fluid. Bernard in 1855 showed instead that it originated in the liver. He did not come to this conclusion easily, though he implied in his published paper that he did; rather it was the result of an involved pathway of reasoning and experiment which has been traced in his laboratory notebooks. 42 Nevertheless by his final set of experiments he established two facts, and at the same time discredited the theory of Dumas and Boussingault and the idea that sugar was formed throughout the entire body. He expressed his two facts in this way. First, animals produce sugar in the organizm; it is always in the liver and in the blood, even of carnivores. "It is perfectly established since my experiments that sugar [glucose] is produced in the animal organism without the intervention of sugars and starches." Second, the glycogenic function is localized in the liver. Blood entering the liver by the portal vein contains no sugar; blood leaving by the hepatic vein contains sugar. He removed the liver from a dog and at once washed it thoroughly with water. T h e washings gave a strong test for glucose. When no more could be washed out, he allowed the liver to stand for twenty-four hours, and again washed it out with water. T h e washings once more contained sugar. He concluded that fresh liver contained sugar and an insoluble substance which was converted into sugar by standing. Since boiling the liver prevented this conversion, a ferment must have produced the reaction. Two years later he announced the isolation of the "glycogenic material." 43 He had expected it to be albuminoid, but it turned out to be similar to vegetable starch both in properties and reactions. Still unable to discard his own form of vitalism, Bernard summed up his theory of carbohydrate metabolism: "The first action, entirely vital, does not occur without the influence of life and is the creation of the glycogenic material in living hepatic tissue. T h e second action, entirely chemical, can be done without vital influence and consists in transformation of glycogenic material to sugar with the aid of a ferment." In order that sugar might appear in the liver, both these actions had to occur. Glycogen was isolated independently at almost the same time

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by V. H e n s e n , a medical s t u d e n t f r o m Schleswig. 44 U n f o r t u n a t e l y f o r H e n s e n , B e r n a r d ' s p a p e r was published first, a n d in acknowledging t h e a d v a n t a g e t h e great physiologist h a d over the u n k n o w n medical student, the latter r a t h e r plaintively r e m a r k e d , " T h u s it is B e r n a r d succeeded almost alone in f i n d i n g the outline of this i m p o r t a n t process f r o m t h e b e g i n n i n g to e n d , a n d I m u s t see that my share in establishing these newest facts m u s t be almost wholly lost." B e r n a r d h a d p r o v e d that the liver was t h e only source of blood sugar, a n d h e also indicated that in muscle glycogen gave rise not to sugar b u t to lactic acid. F u r t h e r progress in c a r b o h y d r a t e metabolism h a d to await t h e elucidation of t h e structures of t h e sugars at t h e e n d of t h e century, chiefly by the work of Emil Fischer. While B e r n a r d was d i p r o v i n g f o r carbohydrates the theory of D u m a s a n d Boussingault that only plants could originally synthesize nutrients, work o n t h e o t h e r f o o d Constituents was also proc e e d i n g vigorously. T h e most influential investigator in this field was J u s t u s Liebig, whose earlier work in p u r e organic chemistry led him into studies of a physiological n a t u r e . I n 1840 h e published his i m p o r t a n t work o n argricultural chemistry, a n d in 1842 h e followed it with his Animal Chemistry, which went t h r o u g h n u m e r o u s editions a n d revisions d u r i n g his lifetime. 4 5 Liebig was f o n d of expressing his ideas in very positive terms, which o f t e n led him into conflict with o t h e r scientists. Many of his writings have a h a r s h , polemical character. H e was actually w r o n g in m a n y of t h e details of his theories, b u t his work r e p r e s e n t e d a great advance over previous studies, especially in r e g a r d to n i t r o g e n c o m p o u n d s . T h e c o n t i n u o u s testing of his theories in the laboratory by himself a n d his students allowed him to correct m a n y of his early e r r o r s in later editions of his books. A n i m p o r t a n t aspect of Liebig's work was his constant use of quantitative calculations in relation to biological processes. H e f o u n d e d most of his theories of p r o t e i n composition a n d reactions o n quantitative analysis a n d m a d e m a n y calculations of t h e a m o u n t of oxygen r e q u i r e d in the combustion of d i f f e r e n t f o o d s u n d e r varying conditions of climate a n d work. A f t e r him physiological chemistry lost t h e largely qualitative character it h a d

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possessed in previous times. 46 H e was also a great popularizer of chemistry, and in his Familiar Letters on Chemistry47 he explained his ideas in readily understandable terms. Liebig drew a s h a r p distinction between the "plastic elements of nutrition," the nitrogenous compounds, and the "elements of respiration," fat, butter, milk sugar, and starch. He believed that the plastic elements m a d e u p the organized parts of the body. H e stated: " T h e r e is, indeed, no part of an organ possessing a form or structure of its own, the elements of which are not derived f r o m the albumin of the blood. All organized tissues in the body contain a certain a m o u n t of nitrogen." 4 8 T h e respiratory foods were never organized but only filled in spaces mechanically in the organized structures. T h e i r function was to supply body heat by combustion. Liebig was convinced that all body heat and motion were produced by combination of carbon or hydrogen of food with oxygen: " T h e mutual chemical action of the constituents of the food and of the oxygen conveyed by the circulation to all parts of the body is the source of animal heat."*9 H e carried out many calculations to show how oxygen was utilized u n d e r varying conditions and to indicate the nutritional value of different foods. T h u s , he stated, "We can prove, with mathematical certainty, that as much flour of meal as can lie on the point of a table knife is m o r e nutritious than five mass [about nine quarts] of the best Bavarian beer." 5 0 H e applied this reasoning to his theories of the behavior of plastic and respiratory substances. Plastic elements could break down, yielding besides carbon dioxide, urea or uric acid. T h e latter two compounds contained relatively little carbon. T h e remaining carbon, passing t h r o u g h the f o r m of "choleic acid" in the bile, was finally oxidized to carbon dioxide by oxygen. 5 1 T h e total a m o u n t of oxygen taken in by the body was a measure of the a m o u n t of nourishment utilized. If insufficient oxygen for combustion to supply the body's need for heat and work was taken in by respiration, residual carbon or hydrogen took oxygen f r o m other oxygenated compounds in the system, and the c o m p o u n d s thus deprived were converted to fat, which contained less oxygen than did proteins or carbohydrates. Said Liebig: "This excess of carbon, as it cannot be

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employed to form a part of any organ [not being a plastic element] is deposited in the cellular tissue in the form of tallow or oil. At every period of animal life, when there occurs a disproportion between the carbon of the food and the inspired oxygen, the latter being deficient, fat must be formed. Oxygen separates from existing compounds, and the oxygen is given out as carbonic acid or water. T h e heat generated in the formation of these two products contributes to keep up the temperature of the body." 52 Thus Liebig fully believed in the conversion of carbohydrates to fats by animals, though he still thought that only plants could originally form the plastic elements. In view of the importance Liebig ascribed to the nitrogenous constituents of the diet, it was natural that he devoted much attention to the nature of proteins. Here he drew at first on the work of Geradus Johannes Mulder (1806-1880), professor of chemistry at the University of Utrecht. Like Liebig, Mulder was a man of irritable temper and strong feelings, and he and Liebig were violent antagonists over a long period. T h e literature is full of their bitter attacks on each other. Nevertheless, the ideas of Mulder formed the basis on which Liebig erected his theories, and the latter utilized much of Mulder's experimental data, not always with proper acknowledgment. 53 By this time, most chemists accepted the existence of four nitrogenous animal products: fibrin, albumin, gelatin, and casein (which had been isolated by Berzelius). One vegetable protein was known, gluten. Mulder began to study silk, and soon came to the conclusion that it contained a second kind of fibrin, which he called fibroin. He decided that all these compounds contained a single radical. The radical theory, then dominant in organic chemistry, held that certain fixed groups could be transferred from one substance to another in organic compounds much as were the elements in inorganic substances. Thus Mulder's theory of a protein radical, identical in all proteins, was a logical part of the chemical thought of the day. Mulder proposed the name protein and from his analytical results he gave the radical the formula C40H62N10O12. He believed that the difference between different proteins depended on the amount of sulfur and phosphorus they contained. Calling the protein radical Pr, he

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wrote the formula for fibrin as Pr + SP, and of albumin as Pr + S2P.54 He thought that plant proteins were taken in by animals and used directly for their own protein needs. In his autobiography, discovered only after his death, he claimed, "One point is certain, that I have been the first who has shown (in 1838) that the meat is present in the bread and the cheese in the grass; that the whole organic kingdom is endowed with one and the same group, which is transferred from plant to animals, and from one animal to another; one group which is first and foremost." 55 These were the ideas that Liebig took over and enlarged. At first he accepted the four classical animal proteins, noting that gelatin was not capable of supporting animal life alone. The other three corresponded to blood constituents and could be used directly for forming organized parts of the body when they were obtained from other animal sources. Soon, however, he realized that gluten was not the only plant protein, and he convinced himself that in plants there existed proteins which were exactly analogous to the major animal proteins. The classical gluten resembled blood fibrin; a portion of plant juice which was coagulated by heat was "absolutely not distinguishable" from the albumin of blood; and the chief nitrogenous substance in seeds of leguminous plants was vegetable casein. These, when obsorbed into the animal, were directly taken up by the blood and distributed to the various organs and tissues where they replaced substances which had been oxidized. In his usual positve style, Liebig wrote, "How admirably simple, after we have acquired a knowledge of this relation between plants and animal, appears to us the process of formation of the animal body, the origin of its blood and of its organs! The vegetable substances which serve for the production of blood, contain already the chief constituent of blood, ready formed with all its elements. The nutritive power of vegetable food is directly proportional to the amount of sanguigenous compounds in it; and in consuming such food, the herbivorous animal receives the very same substances which, in flesh, support the life of carnivores." 56 Because herbivorous animals took in less protein food from their vegetable diet, they had less carbon to be oxidized from this source, but the greater amount of starchy material in their diet made up for this.57

174 Development of Biochemical Concepts In view of the differences in sulfur content of various proteins, Liebig decided in 1845 that Mulder's "protein radical" did not exist.58 He then began to consider possible intermediates in protein structure and reactions. His attention was drawn to the amino acids, though he did not realize their true significance for proteins. The first amino acid to be isolated, cystine, had been obtained from a urinary calculus by William Hyde Wollaston (1766-1828) in 1810. He called it cystic oxide, and neither detected the sulfur in it nor connected it with proteins. In 1819 J. L. Proust (17541826) isolated impure leucine from fermenting cheese, and in 1820 Henri Bracannot (1781-1855) for the first time applied the method of hydrolysis by sulfuric acid to proteins to obtain purer leucine from muscle fiber and wool.59 Since this type of hydrolysis had produced a sugar from starch, Braconnot applied it to gelatin and obtained a sweet substance which he called "sugar of gelatin" (actually glycine), though he noted that it could not be fermented like glucose.60 Mulder in 1838 obtained purer preparations of leucine and glycine by this method. 61 In 1846 Liebig fused cheese with potassium hydroxide and isolated leucine and a new crystalline substance,62 which he later called tyrosine.63 As a result of his studies he decided that leucine and tyrosine were among the most important constitutents of proteins and were involved in their breakdown. Liebig himself used rather drastic methods for studying proteins: alkaline fusion and oxidation with chromic acid. His student, Bopp, applied the method of Braconnot, heating casein with hydrochloric acid to obtain leucine and tyrosine.64 Vickery and Schmidt call this the first recorded successful hydrolysis of a protein by hydrochloric acid.65 The value of this method was finally established by Heinrich Ritthausen (1826-1912). In 1872 he published a book on the proteins of cereals, legumes, and oil seeds. He showed that the best method for characterizing proteins was acid hydrolysis and gave tables of the amino acid composition of different proteins. He was one of the first to emphasize that mild reagents should be employed in studying proteins, and in particular that strong acids and bases should be avoided.66

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Liebig drew many conclusions about the effect of diet and the best diet to be taken under varying conditions. An example of his thinking was that "the proportion of the pastic elements required by the working man in his daily food cannot be less than that which nature herself prepares for the development and growth of the human body, and for its increase in all its parts. Such is the proportion found in human milk. T h e diet of the working man should therefore contain, for four parts of the nonnitrogenous constituents, one part of plastic nutrient matter." 67 Liebig concluded that when the amount of work done is increased, the demand for protein is increased and the amount of protein in the diet should rise. Vickery has summarized the important achievements of Liebig and his students in protein chemistry as follows: his work led to the collapse of the Mulder "protein" theory; he established the existence of four distinct kinds of protein (though he later admitted that different kinds of fibrin existed); he discovered tyrosine; he called for a study of protein decomposition products; he emphasized the importance of protein intermediates. 68 Liebig also realized the importance of inorganic elements in food and particularly stressed the need for phosphorus. He was led to this view because phosphorus was always found in the organized structures of the body: "We must, for the present, be satisfied with deducing, from its constant presence in all the juices and organized tissues of the body, the conclusion that it is indispensable for the vital operations." 69 In a footnote he added that there was evidence that phosphates formed true chemical compounds with albumin. Although the impressive and sometimes erroneous theories which Liebig expressed with regard to the assimilation of foods were themselves important, his laboratory studies and most of the experimental work of his students characterized the properties and reactions of proteins so well that further work in this direction was greatly facilitated. This led directly to the basic investigations of Emil Fischer in this field at the end of the century.

15 Enzymes and Cell Constituents

By the middle of the nineteenth century chemists and physiologists had examined many important biological reactions and had made a beginning in the discovery of some of the mechanisms by which they occurred. Further progress in this direction had to await a fuller understanding of the chemistry of the substances which were involved in these mechanisms. It was necessary to comprehend the nature of the various "ferments" which were concerned in metabolic activities and to know the structures of the major classes of building materials and energy sources utilized by the cells. The advances in organic chemistry after 1860 made study of these problems possible. The work in these directions carried on at the end of the nineteenth and the beginning of the twentieth centuries opened the way to knowledge of the intermediates formed in metabolism between ingested foods and their final oxidation products. T h e task was well under way as the new century began. T h e discovery of diastase by Payen and Persoz had been followed by evidence for the existence of similar substances: the starch-splitting ferments in saliva and pancreatic juice, the emul-

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sin involved in splitting amygdalin, and the pepsin of gastric juice. All these substances could be prepared by extraction of their biological sources with water, precipitation from the solution by alcohol, and resolution in water, without serious loss of activity. They appeared to act by contact and thus were believed to be catalysts in the sense defined by Berzelius. Since they were apparently produced in fluids which did not seem to be parts of specific organs, they were variously called "soluble" or "unorganized" ferments. T h e mechanism of alcoholic fermentation, one of the oldest reactions known to man, did not quite seem to fit into this scheme. This difficulty became particularly apparent in 1836 when Charles Cagniard de Latour (1777-1859) observed that living globules of yeast were always associated with the production of alcohol and carbonic acid in alcoholic fermentation. Since yeast was capable of reproducing itself, it was an organized being, probably of a vegetable nature. His observations were independently confirmed by Theodor Schwann and by Friedrich Traugott Kützing (1807-1893). 1 In their opinion fermentation required the intervention of a living organism. Berzelius rejected this idea completely, holding that his catalytic force was responsible for fermentation and that the yeast was merely a non-living catalyst.2 Support for this view came from an experiment by Eilhardt Mitscherlich (1794-1863), who noted that fermentation seemed to occur only on the yeast surface, and thus the yeast cells acted only by contact. 3 T h e Berzelius theory was taken up and expanded by Liebig, whose great reputation and powerful argumentative ability had a strong effect in scientific circles. However, his views on fermentation were soon challenged by a scientist equally able in experiment and debate, Louis Pasteur (1822-1895). From their controversy on the nature of fermentation came our modern theory of enzymes. Liebig refused to believe that yeast, when alive, had anything to do with fermentation. He was willing to admit that perhaps when the yeast died it released an albuminous substance into a sugar solution and that this substance imparted to the sugar molecules a vibration which resulted in their split into alcohol. 4 This

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was actually only a more sophisticated version of Stahl's theory of fermentation. Liebig and Wöhler ridiculed the living yeast theory by publishing anonymously a satirical description of seeing under the microscope numerous small animals shaped like distilling vessels, which devoured sugar and excreted alcohol and carbonic acid. 5 While Liebig's theory was in many respects incorrect, it had the advantage, as Finegold has pointed out, 6 of keeping all types of enzymatic activity in one conceptual scheme, while Pasteur's theory drew a sharp distinction between soluble ferments and the organized ferments of alcoholic fermentation. Pasteur's early work had been in the field of chemistry. His studies on the optically active tartaric acids and on optical activity in other organic compounds had brought him fame before he began work on fermentation. Though he was later drawn into establishing the new field of bacteriology, he always retained a chemical viewpoint. In 1854 he was appointed professor of chemistry and dean of the Faculty of Sciences at the University of Lille. T h e fermentation of beet sugar to alcohol was one of the chief industries of the Lille area, and this led Pasteur into a study of alcoholic fermentation in 1855. He soon expanded his studies to other types of fermentation and established to his own satisfaction that different organisms were responsible for the various types of fermentation which led to different end products. His first publication in this field concerned lactic acid fermentation. In this paper 7 he presented the ideas which formed the base of all his later work in microbiology. He showed that the organism which caused lactic acid fermentation was living (at this time he called it a yeast). It differed from the yeast which produced alcohol. T h e concluding words of this paper expressed his fundamental ideas, which he later developed but did not essentially change: "In the course of this memoir I have reasoned on the hypothesis that the new yeast is organized, that it is a living being, and that its chemical action on sugar is correlated with its development and organization." He attacked the view of Liebig vigorously. "Anyone who will judge the results of this work and that which I will publish will agree with me that fermentation is correlative with life, the organization of globules, not the death or

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putrefaction of these globules, nor does it appear a contact phenomenon when the transformation of the sugar is accomplished in the presence of a ferment which gives nothing, takes nothing." He always insisted that he was concerned with life, not death. In 1861 he announced a very important discovery. When studying butyric acid fermentation he observed that the "animicules" which caused it grew in the absence of oxygen and were killed by its presence. 8 He at once extended this observation to brewer's yeast.9 He showed that when this organism grew in the absence of air it produced considerable quantities of alcohol but grew slowly. In the presence of air it grew a hundred times as fast but did not produce alcohol. To him this explained the whole "mystery of fermentation." He said: "Some brewer's yeast assimilates oxygen gas with energy when this is free; this proves that the yeast requires it to live and should consequently take it from fermentable materials if refused the free gas; then the plant appears to us as an agent for the decomposition of sugar. For the respiration of its cells it uses the sugar molecules whose equilibrium is destroyed by extraction of a part of their oxygen. A decomposition phenomenon ensues and from this comes the ferment character, which, on the contrary, is lost when the plant assimilates free oxygen gas." In 1863 he rather cautiously suggested in a footnote that the names aerobe and anaerobe be applied to organisms which lived with or without oxygen. 10 This suppression of fermentation in the presence of oxygen is now called the Pasteur effect, though its explanation is considerably more complex than that given by Pasteur himself. Pasteur generalized and summed up his ideas on fermentation in his book on diseases of beer published in 1876: "The essential point of the theory of fermentation which we have been concerned in proving in preceding paragraphs may be briefly put in the statement that ferments, properly so called, constitute a class of beings possessing the faculty of living out of contact with free oxygen, or, more concisely still, we may say fermentation is the result of life without air." 11 Pasteur's views were so revolutionary that they produced controversy immediately. Many criticisms he was able to refute by

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experimental evidence. A number of workers were unable to grow microorganisms in the absence of oxygen, but Pasteur showed that these cases were due to technical difficulties. Eventually even his opponents confirmed his observations in this respect. Other workers, such as Liebig and Moritz Traube (1826-1894), claimed that yeast required the presence of an "albuminous" material if fermentation was to occur. Pasteur thereupon demonstrated that fermentation could take place in a purely inorganic medium. T h e most telling objection, however, was that there could exist in yeast a "soluble" ferment which by its catalytic action could produce fermentation. Traube made this suggestion in 1858, and in 1874 he repeated the theory that an unorganized ferment was responsible for fermentation. He believed that ferments were closely related to proteins. 12 T o Pasteur these were only "hypothetical" ideas. Support for Traube's theory had been supplied in 1860 by Marcellin Berthelot. 13 He showed that, besides alcoholic fermentation, brewer's yeast could bring about inversion of cane sugar, that is, hydrolysis of sucrose to glucose and fructose. He then extracted the yeast with water, precipitated a fraction with alcohol, and when he redissolved this fraction in water, found that it still produced inversion. It was thus a typical "soluble" ferment. He pointed out that it behaved like diastase, emulsin, pancreatic diastase, and pepsin. He said: "Among secreted ferments, those which are soluble can be isolated and purified up to a certain point, in the fashion of immediate, definite ferments. I establish this for the glucosic ferment from brewer's yeast. On the contrary, insoluble ferments are contained in organized tissues and cannot be separated. As to the soluble ferments, we see clearly that the living being is not the ferment, but that which engenders it. Also, the soluble ferments, once produced, exert their action independently of all ulterior vital acts; this action shows no necessary correlation with regard to any physiological phenomenon." Berthelot expressed the opinion that organized ferments probably acted in the same way as unorganized ones, even if they could not be isolated. Pasteur dismissed this claim in a rather high-handed manner: "As for me, when cane sugar and brewer's yeast interact, I call the ferment only that which ferments the sugar, that is to

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say, which produces alcohol, carbonic acid, etc." 14 For Pasteur, the living organism was the ferment. A f t e r the death of Liebig, Berthelot became the chief o p p o n e n t of the Pasteur theory. T h e two m e n engaged in a lengthy polemic in 1878 and 1879. Each accused the other of indulging in unsupported hypotheses. Each was to a considerable extent correct in this. Berthelot's position that fermentation was not a living process could not really be justified until a f e r m e n t could be isolated f r o m yeast and shown to produce alcohol by its own action. In spite of many attempts at this time, no such f e r m e n t had been obtained. Neither m a n knew enough about the intermediates in the reaction to discuss the chemistry involved in a meaningful way. 15 T h u s the debate was inconclusive. However, in the course of it Pasteur m a d e one suggestion which showed foresight, later to be justified. H e wrote: " T h e aerobic being creates the heat it needs by combustion resulting f r o m the absorption of f r e e oxygen gas, the anaerobic being creates the heat it needs by decomposing a material called fermentable which belongs to the kind of substances called explosible, susceptible of giving heat by their decomposition. In the f r e e state the anaerobic being is often so avid for oxygen that simple contact with air burns and destroys it and it is in this affinity f o r oxygen that there undoubtedly resides the first principle of action of microscopic organisms on fermentable materials. Before being able to give heat by their decomposition it is necessary that these materials be caused to decompose." 1 6 H e r e Pasteur was relating his chemical views to the developing subject of biological energetics which was the concern of a n u m b e r of physiologists of the period. T h e systematic nomenclature of the enzymes was developed at this time. Willy K ü h n e (1837-1900) suggested in 1876 that the unorganized ferments which, like invertase, were f o u n d inside the yeast cell be called "enzymes" f r o m the Greek words for "in yeast." 17 This n a m e gradually replaced the older term "ferments." E. P. Duclaux' (1840-1904) in 1883 suggested that the termination -ase be used in the n a m e of enzymes to indicate their character, deriving this f r o m the name diastase, which Payen and Persoz had given to the first enzyme to be isolated. 18 T h e final proof of the identity in fuction of the unorganized

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and organized ferments was given in 1897, when Eduard Buchner (1860-1917) finally isolated "zymase" from living yeast cells and showed that it acted independently of their life processes.19 T h e discovery was accidental. Büchner and his brother Hans (1850-1902), a bacteriologist, were attempting to break up yeast by grinding it with sand in order to obtain a preparation for therapeutic purposes. The yeast juice they obtained decomposed rapidly. Ordinary antiseptics did not prevent this destruction. They therefore added a highly concentrated sugar solution as a preservative. T o their great surprise they observed a strong evolution of carbon dioxide and the formation of alcohol. 20 Eduard Buchner eliminated all traces of yeast cells from the juice by pressing it out with a hydraulic press, and thus proved that the long-sought enzyme could be separated from the living cell.21 The theory proposed by Traube and Berthelot was now established. All fermentations produced by living organisms were due to ferments secreted by the cells.22 T h e distinction between organized and unorganized ferments no longer existed, and all could be called enzymes. T h e complexity of the enzyme systems began to be appreciated at about the time zymase was isolated. In 1897 Gabriel Bertrand (1867-1962) claimed that calcium salts were necessary for the action of pectase on pectins and that manganese was essential for the action of laccase.23 He proposed the name co-ferment for these salts. When Arthur Harden (1865-1940) and William John Young carried out their classic study on the mechanism of yeast fermentation, they noted that the addition of boiled yeast juice, itself inactive, to sugar undergoing fermentation by fresh yeast juice greatly increased the production of carbon dioxide. They showed that this phenomenon was due to the presence of a substance distinct from the enzyme and capable of being separated from it by dialysis. Both the residue, which contained the enzyme, and the dialysate were inactive, but when the two portions were combined, enzymatic activity once more took place. 24 They suggested the use of Bertrand's term "co-ferment" for the substance in the dialysate, saying: "Although not entirely satisfactory, this term may be provisionally applied to activating substances such as those present in liver lipase and yeast juice, until further know-

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ledge of their nature and function permits a more rational terminology." However, the name coenzyme became Firmly established. T h e chemical nature of enzymes remained a problem for many years. T h e high activity of minute traces of enzymes and their great chemical reactivity made isolation and purification very difficult. Doubt as to the possiblility of ever obtaining them pure was often expressed, and numerous theories of their mechanisms of action were proposed. Some thought they were a force which remained around substances which had once been living. Others believed their action was due to radioactivity. 25 A theory which gained wide acceptance was proposed by Richard Willstätter (1872-1942), one of the most influential organic chemists of the early twentieth century. He thought the true enzyme was some very unstable substance of unknown structure which was adsorbed in minute amounts on some colloidal carrier, possibly a protein or polysaccharide, and was stabilized by the carrier. He believed he could prepare solutions of an enzyme which gave no protein tests, and so did not believe enzymes were proteins. 26 This theory delayed an understanding of enzyme chemistry for several years. However, in 1926 James B. Sumner (1887-1955) carried out the first isolation of a crystalline enzyme, urease, obtained from jack bean meal, and demonstrated its protein character. 27 In 1930 John H. Northrop (1891) crystallized pep28 sin, and the following years many enzymes were prepared and studied. All were proteins. In Northrop's book of 1939 he pointed out that enzymes were so active that they could still function in solutions so dilute as not to show chemical tests for proteins. 29 Even before their chemical nature was known, a mechanism for enzyme action had been worked out on the basis of the theory of intermediate compound formation. T h e mathematical formulation of this mechanism by Leonor Michaelis (1875-1949) in 1913 became the basis for later kinetic studies of enzyme action. 30 With the elucidation of many problems connected with enzymes the way was opened for establishing the mechanisms of many metabolic reactions. Before there could be full utilization of the new knowledge, it was also necessary to know the structures of the compounds whose reactions the enzymes catalyzed. Rapid

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progress in this direction was m a d e at t h e e n d of the n i n e t e e n t h a n d b e g i n n i n g of t h e twentieth century. T h e s t r u c t u r e of the fats did not o f f e r great difficulty. T h e i r essential n a t u r e h a d b e e n shown by Chevreul in 1823. It could be clearly expressed as soon as the structural theory of organic chemistry h a d b e e n developed. I n spite of the brilliant work of C l a u d e B e r n a r d o n c a r b o h y d r a t e s and of Liebig o n proteins, detailed explanations of t h e structures of these classes were lacking. Establishment of t h e chemical structures of both carbohydrates a n d proteins was largely d u e to t h e synthesizing skill of Emil Fischer (1852-1919). Clarification of t h e structures of the sugars was impossible until van't H o f f a n d Le Bel h a d i n t r o d u c e d the concept of asymmetric carbon a t o m s a n d stereochemistry in 1874. D u r i n g the d e c a d e of t h e eighties Heinrich Kiliani (1855-1945) developed his cyanohyd r i n m e t h o d of l e n g t h e n i n g the chain in carbohydrates. 3 1 Using this m e t h o d a n d employing his own laboratory skill, Fischer was able to work o u t t h e structures of t h e m o n o - a n d disaccharides, a n d even to synthesize some of t h e biologically i m p o r t a n t ones. 3 2 His work in this field culminated in t h e d e t e r m i n a t i o n of t h e s t r u c t u r e of glucose, t h e most i m p o r t a n t sugar f r o m the standpoint of biochemistry. 3 3 T h e chemistry of the proteins was f a r m o r e complex a n d was correspondingly difficult to work out. Many of these complexities were realized by K ü h n e in his studies of proteolytic action. A stud e n t of B e r n a r d , K ü h n e , h a d c o n t i n u e d t h e latter's work on pancreatic juice, especially with r e f e r e n c e to its action on proteins. 3 4 I n the course of this work h e discovered the enzyme trypsin a n d showed that it attacked p r o t e i n f r a g m e n t s which had resulted f r o m t h e action of pepsin o n t h e original protein. 3 5 H e t h e n u n d e r t o o k a lengthy series of e x p e r i m e n t s o n proteolytic digestion by the action of pepsin and trypsin, in collaboration with his f o r m e r s t u d e n t , Russell H . C h i t t e n d e n (1865-1943), who established the first laboratory of biochemistry in t h e U n i t e d States at Yale. 3 6 K ü h n e worked at H e i d e l b e r g a n d C h i t t e n d e n at Yale, b u t between 1883 a n d 1890 they published a series of j o i n t p a p e r s both in G e r m a n in t h e Zeitschrift fur Biologie a n d in English in the

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American Chemical Journal or the Transactions of the Connecticut Academy of Arts and Sciences.37 They noted that a large number of relatively low molecular weight protein derivatives were produced, and that the products formed under the influence of the two enzymes differed. They named these substances peptones and gave them specific names derived from their sources: albuminoses, globuloses, myosinoses, and so on. Their original hope that these products would throw light on protein structure was not realized, since the substances were too indefinite in composition to yield specific information as to their nature. However, these studies did reveal more clearly the complexity of the protein molecule. 38 They also indicated the fact that the end product of protein hydrolysis was often an amino acid. By 1885 the number of known amino acids had increased to ten, seven of which were associated with proteins. Between 1888 and 1903 ten more were discovered, all in protein hydrolysates. However, the manner in which they were linked in proteins was not at first clear. In 1888 Curtius and Goedel 39 described the cyclic anhydride of glycine (then called glycocoll) and indicated that it contained a type of bonding of a CO and an NH group which Curtius had found in hippuryl glycine in 1882. Soon after this Emil Fischer developed a method for separating amino acids by fractional distillation of their ethyl esters. 40 In 1901 he turned his attention to the glycocoll anhydride and showed that the ring could be split by heating the compound with concentrated hydrochloric acid. This resulted in formation of a substance which he called "the first anhydride of glycocoll" and to which he ascribed the formula NH 2 CH 2 CONHCH2COOH. 4 1 He suggested that glycine was a better name than glycocoll and so the compound should be called glycyl glycine. Using his ester distillation method, Fischer was soon able to prepare alanyl alanine and leucyl leucine. 42 The -CONH- bond was thus established as the characteristic link between the amino acids, and Fischer named it the peptide bond. Continuing his studies, he suggested the name polypeptides for low molecular weight substances with the properties of proteins. 43 At about the same time Franz Hofmeister (1850-1922), after a thorough review of protein chemistry,

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independently concluded: "On the basis of the facts given, we can regard the proteins chiefly as condensations of α-amino acids in which the group CO-NH-CH is regularly repeated." 4 4 Fischer went on to synthesize more and more complex polypeptides. His work culminated in the preparation of the octadecapeptide Meucyl-triglycyl-/-leucyl-triglycyl-/-leucyl-octaglycyl-glycine, which he described in 1907. 4 5 His work established the essential structure of the proteins, though much investigation for their separation and purification remained to be carried out. T h e nature of the nucleic acids, also major cell constituents, was gradually worked out during the same period. Their complexity offered a challenge to the organic chemists to determine their structure, while their function was an even greater problem for the biochemist. Active study of these substances began in 1868. In that year Friedrich Miescher (1844-1895) made a chemical examination of pus cells obtained from surgical bandages. He submitted the intact cells to the digestive action of artificial gastric juice, which left the cell nuclei as an insoluble gray powder. From this he isolated an alkali soluble fraction which gave protein color tests and contained a considerable amount of phosphorus. H e called the substance nuclein. He reported his discovery to his teacher, Felix Hoppe-Seyler (1825-1895), the leading physiological chemist of the day. Hoppe-Seyler was extremely doubtful of the existence of so much organically bound phosphorus in a biological material, even though Fourcroy and Vauquelin had demonstrated that such bonding could occur, Liebig had discussed it, and HoppeSeyler himself had previously isolated lecithin. He therefore spent two years in checking the work of Miescher, using yeast as the source of nuclein. When he was convinced of the accuracy of the work, he published Miescher's paper along with an account of his own study. 46 A period of active investigation of nuclein began. Miescher knew that salmon migrating to their spawning grounds contained large amounts of nuclein in their reproductive tracts. At his request J . Piccard made an extensive study of salmon sperm. 4 7 He was able to separate the protein from the phosphorus-containing fraction, and in the latter he noted the presence of guanine, xanthine, and sarkin, as hypoxanthine was

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then called. This established the presence of purine derivatives in nuclein, though he did not realize that the oxidized purines xanthine and hypoxanthine were secondary derivatives from the then unknown adenine. This work was taken up by Albrecht Rossel (1853-1927) in 18 7 9. 48 In 1882 he showed that guanine was present in yeast nuclein, 49 and in 1886 he isolated and named adenine, whose oxidation to hypoxanthine he demonstrated. 50 He expressed the opinion that adenine was probably present in all cells. In 1889 Altmann described methods for separating nucleic acids, as they were now called, from the protein. He obtained such acids from yeast, thymus gland, egg yolk, and salmon sperm. 51 Using Altmann's methods, Kossel was able to discover the pyrimidine bases in nucleic acids from various sources. With Albert Neumann he discovered thymine in 18 8 3 52 and cytosine in 1894. 53 His student Ascoli discovered uracil in 1900.54 Kossel was unable to identify the carbohydrate portion of the nucleic acids, however. In the first decade of the twentieth century a sharp distinction was drawn between nucleic acids from plant and animal sources. 55 It was felt that two distinct acids existed, and these were usually referred to as yeast and thymus nucleic acids. It was known that the latter contained thymine and the former uracil, while the remaining bases guanine, adenine, and cytosine as well as phosphoric acid were common to both. It was believed that the sugar of the yeast acid was a pentose and that of the thymus acid was a hexose. At this time a long investigation of the nucleic acids was begun by Phoebus A. Levene (1869-1940) and his students. Levene and Mandel partially hydroloyzed thymus nucleic acid and obtained a substance whose complete hydrolysis yielded phosphoric acid, thymine, and a "hexose" which they thought was levulinic acid. 56 They called this a nucleotide and recognized that it was an intermediate in the formation of nucleic acids, which were therefore polynucleotides. Levene probably never realized what a high molecular weight they actually had. In the next year Levene and Jacobs 57 suggested that the compound of a base and a sugar, but free from phosphoric acid, be called a nucleoside. In the same paper they showed that the sugar of yeast nucleic acid was ribose,

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and they proposed that in nucleic acids the mononucleotides were linked through the hydroxyl radicals of the phosphoric acid groups. In 1912 Levene and Jacobs suggested that the nucleic acids existed as repeating groups of four nucleotides, each containing one of the four bases, so that the tetranucleotide groups held all the constituent bases. 58 This rigid structural limitation, as long as it was accepted, ruled out any possiblility of developing a concept of a genetic function for the nucleic acids. T h e magnitude of the molecule was not realized. T h e identification of the sugar in thymus nucleic acid was not accomplished for nearly twenty years. In 1929 Levene and London 5 9 isolated a nucleoside from thymus nucleic acid, which they showed was a guanine deoxypentoside. In the next year Levene, Mikeska, and Mori identifiied the sugar as 2-deoxyribose. 60 The true size and complexity of the nucleic acids was slowly realized. In 1924 Hammarsten 6 1 recognized from osmotic pressure, viscosity, and other physical properties of their salts that they must be substances of a size of an entirely different order of magnitude from neutral proteins. By 1939 even Levene saw that they could have nolecular weights of one or two million. 62 The first major indication of their biological significance came after Stanley in 1935 crystallized tobacco mosaic virus and showed that it was a protein. 63 It was identified as a nucleoprotein two years later by Bawden and Pirie. 64 The full importance of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) for heredity and protein synthesis was realized only after the middle of the century.

16 Energy Production and Biological Oxidations

T h e source of animal heat had been one of the major problems of biology from the time of the Greeks, but a rational understanding of it was not possible until the discovery of oxygen and carbon dioxide. After these had been identified, it became possible to recognize the close relation between respiration and combustion, 1 and both Crawford and Lavoisier not only emphasized this relation but began to consider the amounts of heat produced in each process. The basis for animal calorimetry was laid by these men (Chapter 11). They stated definitely that the total amount of heat produced in a chemical reaction was the same, no matter what intermediate pathways the reaction followed. T h e theory of heat as a material substance, caloric, however erroneous, did not prevent valuable laboratory studies which confirmed this principle. T h e serious error of the period was the idea, expressed by both Crawford and Lavoisier, that combination of carbon and oxygen took place in the lung, and the heat produced was distributed to the rest of the body by the blood.

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This idea was shown to be incorrect by the 1837 studies of Heinrich Gustav Magnus (1802-1870), though his own theory was equally incorrect.2 He developed accurate methods for determining the amounts of oxygen and carbon dioxide in the blood and pointed out that the redder color of arterial blood came from the presence in it of a greater amount of oxygen than in venous blood. This convinced him that the oxygen somehow combined with the blood pigment, since "I know of no case in which a liquid changes color by absorption of a gas, except when the appearance of absorption comes from chemical combination. It therefore seems very likely to me that the change in color of the blood depends on absorption followed by chemical binding." He believed that combustion of carbon took place in the blood rather than in the lungs. In the early years of the nineteenth century the industrial revolution was reaching its height and men's minds were turning strongly to mechanical explanations of natural phenomena. The steam engine was the most spectacular product of this period. Its operation emphasized that heat could produce work. More and more the old theory of caloric was called into question. The imponderable fluids of the eighteenth century no longer offered a satisfactory explanation of nature. Physicists were now thinking in terms of "force" or energy, as it came to be called. It was a physiological observation, however, that brought about the formulation of the great generalization, the principle of the conservation of energy, upon which both physical and biological science were to rely in the latter part of the century. In July of 1840 Julius Robert Mayer (1814-1878), a ship's physician, performed the routine operation of bleeding a seaman in the port of Surabaya, Java. He observed that the venous blood which he drew in this tropical climate was a brighter red than was usual in Europe. The relation of blood color to temperature had been observed before, but no one had drawn an important conclusion from it. It was Mayer, in a flash of insight, who recognized the significance. 3 He was aware that in a tropical climate less heat was required for metabolic activity and for work, and he knew that the redder blood meant more unused oxygen and so less combustion. Thus a certain amount of heat corresponded

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to a certain amount of work. Mayer went on to deduce the physical consequences of this idea. His first paper on this subject was rejected for publication by Poggendorf, but in 1842 Liebig published the classic paper, "Observations on the Forces of Inanimate Nature." 4 The physical consequences of the law were much in Mayer's mind, and he wrote, "In water mills the continual diminution in bulk which the earth undergoes, owing to the fall of water, gives rise to motion which afterwards disappears again, calling forth unceasingly a great quantity of heat; and inversely the steam-engine serves to decompose the heat again into motion or the raising of weights. A locomotive engine with its train may be compared to a distilling apparatus; the heat applied under the boiler passes off as motion, and this is deposited again as heat at the axles of the wheels." This analogy to the steam engine continued to dominate the thoughts of biologists. Twenty-five years later Voit and Pettenkoffer, discussing the biological utilization of energy, remarked, "As coal, burned under a boiler, moves a steam engine, so do fats and carbohydrates by their oxidation in the body to carbon dioxide and water yield the power for our mechanical performance." 5 Methods for determining the mechanical equivalent of heat were soon worked out by the physicist James Prescott Joule (1818-1889), and a full treatment of the theory was presented in 1847 by the physiologist and physicist, Hermann Helmholtz (1821-1894). 6 Once this principle was fully recognized it became the task of the chemist to determine the full course of the chemical reactions by which foodstuffs were converted to carbon dioxide and water with the production of energy. In 1839 Boussingault had designed a series of experiments on a milk cow to prove that the nitrogen of the air was not used for nutritive purposes. 7 In the course of this work he compared the quantity and nature of the elementary material which was taken in as food with the quantity and nature of the elementary material eliminated in urinary and digestive products and milk. He then calculated by difference the amount of food eliminated in respiratory products. He thus introduced the first effective balance experiments in animals and demonstrated the existence of the nitrogen cycle.8

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T h e method was taken over by Liebig, who made balance studies on humans, a group of soldiers of the Grand Ducal Guards of Hesse-Darmstadt. T h e results were summarized by his student, Carl Voit (1831-1908) as follows, "Liebig was the first to establish the importance of chemical transformations in the body. He stated that the phenomena of motion and activity which we call life arise from the interaction of oxygen, food, and the components of the body. He clearly saw the relation between metabolism and activity and that not only heat, but all motion derived from metabolism. H e investigated the chemical processes of life and followed them step by step to their excretion products." 9 In order to carry on the work begun by Liebig, it was essential to determine the behavior of the respiratory gases and their interrelations. In 1849 Victor Henri Regnault (1810-1878) and Jules Reiset (1818-1896) developed a technique for such studies. 1 0 They placed a number of animals of various species under a bell j a r containing a substance which absorbed carbon dioxide and an apparatus for admitting fresh oxygen when needed. This permitted measurement of oxygen used and carbon dioxide given off. Although their results did not lead them to important generalizations, their method became the basis for further work on respiration. T h e full significance of the gaseous elements in metabolism was realized by Carl Voit. He found that all the nitrogen in the body came from foods and that a condition of nitrogen equilibrium could be established when the level of nitrogen intake was kept constant. He stated: "I can show that in a few days all the nitrogen of an adequate diet in dogs can be recognized in the urine and feces." 1 1 With Max von Pettenkoffer (1818-1901) he constructed a calorimeter of sufficient size to accommodate a man. T h e cost of this apparatus was supported by King Maximillian II of Bavaria. 1 2 In this direct calorimeter they showed for the first time that by determination of oxygen absorbed, carbon dioxide given off, and nitrogen excreted it was possible to calculate the type and amount of foods oxidized in the body. 1 3 In this work they showed that Liebig's idea of an increased demand for protein with increased muscular work was incorrect. Carbohydrates and fats accounted for the extra energy expended.

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Voit in his necrology of Pettenkoffer 14 summed up the results of these studies: "Imagine our sensations as the picture of the remarkable processes of metabolism unrolled before our eyes, and a mass of new facts became known to us! We found that in starvation protein and fat alone were burned, that during work more fat was burned, and that less fat was consumed during rest, especially during sleep; that the carnivorous dog could maintain himself on an exclusive protein diet, and if to such a protein diet fat were added, the fat was almost entirely deposited in the body; that carbohydrates, on the contrary, were burned no matter how much was given, and that they, like fat, protected the body from fat loss, although more carbohydrates than fat had to be given to effect this purpose; that the metabolism in the body was not proportional to the combustibility of the substances outside the body, but that protein, which burns with difficulty outside, metabolizes with the greatest ease, then carbohydrates, while fat, which readily burns outside, is the most difficultly combustible in the organism." Workers in this field utilized the ratio of carbon dioxide exhaled to oxygen absorbed in many of their calculations. In 1877 E. Pflüger (1829-1910) included this ratio in a table column which he headed "respiratory quotient." He explained, "The expression 'respiratory quotient' used in this table means the ratio of oxygen in the carbonic acid to the oxygen used in the same time. I choose the term 'respiratory quotient' as an abbreviation for physiology in place of the often used CO2/O." He called this ratio "a constant of nature." 15 He was immediately challenged by a certain H. Senator, who pointed out that it was not a constant. In defending himself, Pflüger replied 16 that he had meant the ratio by weight, which was 44 to 16, but he recognized that if volumes were used, the ratio was not a constant. He showed that it could be employed in the manner of Voit and Pettenkoffer to determine the amount and type of food utilized since each type of food had its own respiratory quotient, 1.0 for carbohydrates, about 0.80 for proteins, and about 0.70 for fats. The simpler indirect method of calorimetry is based on this, and the convenience of the term has assured its use ever since. Further extensive studies of this type were carried out by Voit's

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student, Max Rubner (1854-1932). He built an animal calorimeter in which he could measure accurately the amount of heat produced in twenty-four hours. By comparison of the value he obtained with that calculated by the method of Voit and Pettenkoffer he confirmed the law of conservation of energy for living organisms and proved that metabolism, the cause of the motion of life, was the source of the heat produced by the body. 17 Rubner also discovered the specific dynamic action of foodstuffs, stating that "individual substances show a specific ability to stimulate heat production." 18 He supplied the evidence upon which the isodynamic law was formulated. 19 This states that foodstuffs can replace each other in the diet in accordance with their caloric value. Later discoveries of vitamins and mineral metabolism showed the limitations of this law, but its general validity makes it still one of the cornerstones of dietetics. In order to clarify the nature of heat production in the animal, it remained necessary to locate the site of such production, to determine how oxygen reached this site, and to work out the mechanism by which metabolic reactions produced heat. The solution of these problems took the rest of the nineteenth century and continued into the twentieth. Even in the eighteenth century there had been indications that oxidation could occur in the tissues. Spallanzani in his studies on respiration in insects and mollusks had suggested that the tissues and organs of these animals gave off carbon dioxide, but this work was generally neglected. 20 In 1850 Georg Liebig (1827-1903), the son of Justus Liebig, showed that in an atmosphere containing oxygen a frog muscle retained the ability to twitch longer than when oxygen was absent, as in pure nitrogen, hydrogen, or carbon dioxide. He concluded that muscle tissue must respire. 21 Traube confirmed this observation, stating that the work of the muscle is a respiratory act. He assigned three different functions to respiration: cell formation, muscle activity, and heat production, and added, "truly, the story of oxygen comprises the story of organic life." 22 The fact that the heat production from respiration took place in the tissues was finally established by the work of Pflüger. In 1872 he showed that gases diffused from and into the blood in the capillaries and

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stated that the living cell governs the amount of oxygen used, rather than does the oxygen content of the blood. 23 He repeated and strengthened these arguments three years later. 24 For those interested in the function of the blood the emphasis now shifted to a consideration of how the gases were transported. It was known that the red pigment was somehow related to oxygen content. 25 In 1862 Hoppe (who did not assume the familiar double name by adding that of his guardian, Seyler, until 186426) noted the characteristic absorption spectrum of oxyhemoglobin. 27 Two years later he isolated the pigment as a crystalline compound which he called hematoglobulin or hemoglobin, since hematin could be split from the protein by treatment with alkali. T h e hematin contained nitrogen and iron. Hoppe-Seyler did not demonstrate the reversible reduction of the compound. 28 . This was done in the same year by G. G. Stokes (1819-1903). In studying the change in color from arterial to venous blood, Stokes demonstrated the oxidation-reduction of the pigment. He wrote: "We may infer from the facts above mentioned that the colouring matter of blood, like indigo, is capable of existing in two states of oxidation, distinguished by a difference of colours and in a fundamental difference in the action on the spectrum. It may be made to pass from the more to the less oxidized state by the action of suitable reducing agents, and recovers its oxygen by absorption from the air." 29 T h e nature of the active portion of hemoglobin was essentially worked out by William Küster in 1913 when he determined almost the complete structure of the porphyrin ring 30 and the final proof of structure and synthesis of a large number of porphyrins were carried out by Hans Fischer (1881-1945) and his co-workers. 31 Oxygen transport was thus localized in the blood and oxidation of food in the tissues. T h e mechanisms of the oxidations remained unclear. However, almost all chemists felt that metabolites had to be oxidized by some form of activated oxygen. T h e influence of Lavoisier and his ascription of a central position in chemistry for oxygen remained strong. T h e chief problem, as the chemist saw it, lay in the different behavior of foodstuffs

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inside and outside the body. T h e development of the concept of enzymes began to make the processes of metabolism more understandable but failed to explain the role of oxygen. An early attempt to clarify its function was made by Christian Friedrich Schönbein (1799-1868) after his discovery of ozone. 32 He was convinced that this was the active form of oxygen which could explain all types of oxidation. He devoted most of his life to the subject of oxidation and spoke of oxygen as "my chemical hero" and "the great power of the chemical world." 33 He worked chiefly with inorganic compounds and confessed to his friend Faraday that he purposely tried to avoid organic chemistry, feeling that he was not qualified to plunge into its mysteries. However, in 1856 he was led by his own observations into speculations on the mechanism of biological oxidations. He discovered in certain mushrooms a colorless substance which could be oxidized to a blue compound, much as gum guaiacum was oxidized by ozone. Therefore he felt that the mushrooms contained an "organic matter" which "enjoys the remarkable power of transferring Ο into Ο [his symbol for active oxygen] and forming with the latter a compound from which Ο may easily be transferred to a number of oxidizable matters, both of an inorganic and an organic nature, and I must not omit to state that the peculiar agarious matter, after having been deprived of its O, may be charged with it again by passing through its solution a current of air." Schönbein concluded that "the organic matter in question is a true carrier of active oxygen, and therefore, when charged with it, an oxidizing a g e n t . . . Now in a physiological point of view, the existence of such an organic substance is certainly an important fact, and seems to confirm an old opinion of mine, according to which, the oxidizing effects of atmospheric oxygen (of itself inactive) produced upon organic bodies such as blood, etc., are brought about by means of substances having the power both of exciting and carrying oxygen." 34 He observed that this power was lost when the solution was heated. Such an idea of an oxygen carrier was made more precise two years later by Moritz Traube. He was sure that ferments were individual chemical substances of a protein nature, acting,

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"perhaps, with participation of oxygen." Various ferments had the power in different degrees of taking up oxygen and carrying it over to other bodies, thus being themselves reduced. By again taking up oxygen the process could be continued. "In this way behave all ferments which carry over free or bound oxygen in almost endless amounts to other bodies, that is, which act as fermenting or putrefying agents." He called this process slow combustion. 35 A slightly different theory of oxygen activation was proposed by Hoppe-Seyler. He believed that nascent hydrogen attached to a molecule of oxygen, splitting out one atom to form water, while the other became activated and could form hydrogen peroxide with a water molecule, ozone with oxygen, or could oxidize an oxidizable compound. 3 6 Thus, in the 1870's the idea of a transferring substance which permitted continuation of a reaction had become well established. Although attention continued to be centered on oxygen, a possible role of hydrogen was also mentioned. However, the discovery of the role of iron in hemoglobin as the oxygen carrier of the blood led to a search for similar iron compounds in the tissues. In 1884 Charles A. MacMunn (1852-1911) reported the discovery of an iron-containing pigment in muscle tissue. He identified it by its characteristic spectrum and called it myohaematin. He was never entirely sure of its identity, and other workers believed it was impure hemoglobin or myohemoglobin. Hoppe-Seyler in particular discounted its significance. In consequence MacMunn's report was disregarded for many years. 37 The importance of iron was stressed in the early part of the twentieth century by Otto Warburg (1883-1970). He believed that cellular oxidation was carried on by a "respiratory ferment," the active portion of which resembled the hematin of hemoglobin. In its fully developed form, his theory held that biological oxidations involved a nonspecific surface force which held the metabolite to the solid part of a cell. On this surface was located the catalytic iron-containing respiratory ferment which permitted the reaction to occur: "Iron is the oxygen carrying portion of the respiratory ferment; the respiratory ferment is the sum of all catalytically

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active iron compounds which occur in the cell."38 There was only one respiratory ferment, but a multitude of oxidases could be formed from its transformation and decomposition products. 39 Warburg used as one of his main pieces of evidence for the active iron in the ferment the fact of its inhibition by cyanide. While Warburg was stressing the importance of oxygentransporting systems, a new approach to the theory of biological oxidations was made in 1913 by Heinrich Wieland (1877-1957). Instead of looking for oxygen-activating enzymes, he called attention to the fact that in organic compounds removal of hydrogen was an oxidation. Therefore he felt that attention should be directed to a group of enzymes which he called dehydrases. These, he believed, activated hydrogen in the oxidizing compound and permitted its removal. Such a reaction could account for many cases of inorganic and organic oxidations. 40 T h e theory was established experimentally by Torsten Ludvig Thunberg (1873-1952). Beginning in 1917, Thunberg showed that in the reduction of methylene blue in a vacuum, a hydrogen donor was required, the dye acted as a hydrogen acceptor, and an enzyme was essential. He suggested the name dehydrogenase, rather than dehydrase, for the enzyme, and he found enzymes of this type in all living cells he studied. In the investigation of the oxidation of succinic to fumaric acid he noted that the reaction in an isolated system was not inhibited by cyanide, but in cells it was. He concluded that small amounts of "spontaneous activation" of oxygen must occur. 41 There might be a link between oxygen and hydrogen activation after all. Nevertheless the various theories of biological oxidation led to a number of polemical discussions in the 1920's and for a time it seemed that the differing views could not be reconciled. T h e major problem was that the organic chemists thought of oxidation-reduction in terms of hydrogen transfer, while the inorganic chemists thought of electron transfers. If the chief oxidative enzyme was Warburg's iron-containing substance, which had not been specifically identified, there seemed no place for Wieland's dehydrogenases. T h e turning point came with the work of David Keilin (18871963). In 1925 he reported the discovery in a wide variety of cells

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of an iron-containing pigment which could undergo reversible oxidation and reduction. From the spectra he identified three closely related substances which he called cytochromes ("cellular pigments"). 42 He showed that these were the substances which MacMunn had called myohaematin. Warburg had not at first accepted Wieland's dehydrogenation theory and was not now inclined to accept Keilin's work. The latter went on to show that the cytochromes occupied a place intermediate between the dehydrogenation reactions and the action of Warburg's respiratory enzyme, which Keilin at first called indophenol oxidase (now cytochrome oxidase). T h e identification of myohaematin, respiratory enzyme, and indophenol oxidase as one and the same substance brought the ideas of Wieland, Thunberg, and Warburg into agreement. As Keilin said, "Cytochrome therefore acts as a carrier between two types of activating mechanisms in the cell: (1) the dehydrase activating the hydrogen of organic molecules; and (2) the indophenol oxidase activating oxygen. Cytochrome thus acts as a hyrogen acceptor which is specifically oxidized by the indophenol oxidase." 43 Once he was convinced of this, Warburg went on to identify the hydrogen-transporting systems. In 1932 he discovered the "yellow enzyme," the first of the flavo complexes. 44 He then studied a second system, coenzyme I, in which he identified nicotinic acid as a constituent 45 and whose structure and function he explained in 1935.46 It was now possible to picture the whole series of reactions involved in formation of water from a metabolite. In terms of oxidation-reduction potentials the pyridine nucleotides and the flavoproteins fell at the negative end of the scale, the cytochromes higher, and finally the cytochrome oxidase at the highest potential reacting with oxygen. The concept of a chain of transfers, each yielding energy, was firmly established, and was graphically expressed by Szent-Györgyi in 1939: "If you can imagine an apparatus producing the donator at a high rate, taking off its H, dealing with the residue, if you can follow this Η in your imagination, shooting through the long chain of reactions, giving up its electron in the end, then follow the electron as it continues its journey until it reaches O2 streaming constantly into the cell, if you can add to this picture the phosphoric

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esters formed all along the way, and still leave room for other forms of bound energy yet unknown, bound energy reaching those points of the cell which use this energy and perform with it equally complicated functions; if you can imagine all this in full, simultaneous and harmonious actions, then you have the first inkling of that most wonderful organization and activity the sum total of which we call by that one simple little name — Life." 47

17 Intermediary Metabolism

By the end of the nineteenth century physiologists and physiological chemists had defined fairly clearly the nature of the metabolites of which the body was constructed and from the oxidation of which it obtained its energy. The initial and final products of metabolism were well known, but very little was understood of the steps which lay between. T h e physiological viewpoint was no longer adequate, since only by chemical methods could the facts of intermediary metabolism be established. T h e final examples of the purely physiological outlook were represented by the views of the physiologists Hermann and Pflüger. They knew that chemical substances were involved in metabolism and that the changes of these substances must be due to chemical reactions, but they had no comprehension of the complexity of these reactions. Instead they simply assumed the existence of large molecules, probably analogous to the proteins, which somehow decomposed, giving rise to energy, carbon dioxide, and water. Hermann called such molecules "inogen." Pflüger thought of a "giant molecule" which multiplied through polymerization. This concept was developed in detail by Max Verworn (1863-1921), who assumed the existence of certain "living pro-

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teins," which he called biogens. These could convert nonliving proteins into molecules like themselves. As a typical physiologist of his day, he assumed that protoplasm, "a morphological, not a chemical conception," was the arena in which life occurred. 1 This can be considered one of the last attempts to impose vitalism on biochemistry. It was apparently still an appealing idea, however, for even in 1921 the noted English biochemist, Frederick Gowland Hopkins (1861-1947) felt it necessary to attack the theory as futile and to point out the path by which biochemists could unravel the mechanism of metabolism. He said that all theories based on the concept of a living molecule, or biogen, "make no real attempt to explain the unknown in terms of the known. They escape from the hard task of analysis by falling back upon the properties of an entity to which, since it is wholly imaginary, any attribute may be ascribed." He pointed out the only path which could lead to success: "The alternative view is that the living cell (or an equivalent structure) is itself the unit. T h e manifestations of life viewed from this standpoint depend upon changes undergone by diverse molecules of a kind which need not elude ordinary chemical studies. Such molecules of an order common to other non-biological chemical events, take part in diverse chemical reactions which, though they may occur in the colloidal milieu, are themselves ordinary in the sense that they can—individually at any rate—be studied by the recognized methods of chemistry. On this view, the essence of what is peculiar to the cell as a chemical system lies not in the nature, but in the organization of its processes." 2 It was the realization of these facts which converted physiological chemistry into biochemistry, essentially a new science. One of the greatest successes of the first half of the twentieth century was the discovery of the metabolic path of carbohydrate oxidation. T h e establishment of this complex mechanism made possible a deeper understanding of the intermediary metabolism of fats and proteins as well. The initial studies in this field were carried on independently by two groups, one studying alcoholic fermentation, the other muscle metabolism. Eventually the members of the two groups realized that they were investigating essentially the same phenomena. They then joined forces and rapid progress was made.

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T h e first major discovery was that of Harden and Young in 1905 and 1906. Their finding that a coenzyme participated in yeast fermentation has already been mentioned. T h e other important observation in their work, one which assumed greater and greater significance as investigations continued, was the fact that addition of phosphate to yeast juice caused a marked increase in production of carbon dioxide. 3 In their first paper they did not identify the form in which the phosphate acted, but they suggested that "it exists in combination with glucose, probably in the form of a phosphoric ester." By 1908 they had proved that a phosphate ester was present. 4 They were convinced that it was a hexose diphosphate, though even as late as 1914 there were those who thought the substance was a mixture of two triose phosphates. 5 T h e view of the discoverers was finally accepted, and the compound, fructose-1,6-diphosphate, has ever since been known as the Harden-Young ester. At almost the same time Walter Morley Fletcher (1873-1933) and F. Gowland Hopkins showed that under anaerobic conditions, excised frog muscle spontaneously evolved lactic acid, though in the presence of oxygen no lactic acid was formed. Exercising the muscle to produce fatigue led to rapid accumulation of the acid. 6 T h e attention thus drawn to lactic acid led to the conclusion that the chief chemical process in muscle was the conversion of glucose to this acid. T h e analogy between lactate formation in muscle and lactic fermentation in yeast led investigators between 1910 and 1920 to conclude that the two processes were either similar or identical. Evidence for this view was soon forthcoming. Gustav Georg Embden (1874-1933) noted that yeast juice and working muscle produced the same intermediate, which he believed to be glyceraldehyde. 7 Otto Meyerhof (1884-1951) found a common coenzyme in fermentation and respiration. 8 Embden and Laquer in 1914 found a phosphorus compound in muscle press juice which caused production of lactic acid. 9 They called it lacticidogen and three years later identified it as a hexose monophosphate. 1 0 It was actually a mixture of several such esters, but it was called the Embden ester, a name which was applied for several years to chemically unspecified hexose monophosphates. T h e individual esters were subsequently separated and identified. Fructose-

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6-phosphate (Neuberg ester) was isolated in 1918 by Carl Neuberg (1877-1956).11 In 1922 Robert Robison (1883-1941) discovered a hexose monophosphate which proved to be glucose6-phosphate (the Robison ester).12 Finally the Cori ester, glucose1-phosphate, was obtained in 1936 by Carl Ferdinand Cori (1896) and his wife, Gerty Cori (1896-1957).13 In 1920 Meyerhof showed that in frog muscle lactic acid formation and disappearance of reserve carbohydrate occurred simultaneously.14 In 1924 he reviewed the evidence for a common role for phosphates in yeast and muscle metabolism.15 He was able to conclude: "To come back to the question what significance might be attached to the co-enzyme common to respiration and fermentation, we may perhaps suggest that it could possibly have a share in the esterification of organic compounds with phosphoric acid. Doubtless some substances become more unstable by such combination . . . May I make the bold hypothesis that on the one hand the animal body makes fats and carbohydrates accessible to oxidation by combining them with phosphoric acid, whereby they become more labile, and on the other hand, that proteins can only burn in cells by being split up into amino acids?"16 The sources of the phosphate groups were soon to be identified. In 1927 Eggleton and Eggleton reported the presence in muscle of a labile phosphorus compound which they called "phosphagen." 17 In the same year Fiske and Subbarow identified this as a phosphorus derivative of creatine, 18 and two years later 19 they published a long paper on the chemistry of creatine phosphate. The ultimate source of the phosphate groups, adenosine triphosphate (ATP), was discovered independently in 1929 by Karl Lohmann (1898- )20 and by Fiske and Subbarow.21 In 1926 Meyerhof demonstrated that glycogen in muscle was split by enzymes to two molecules of lactic acid per molecule of hexose.22 He stressed the identity of the reactions of glycogen in muscle and glucose in yeast. This similarity became steadily clearer. By 1933 Embden and his co-workers had shown that in the later stages of anaerobic carbohydrate metabolism large amounts of phosphoglyceric acid were formed, and this was converted directly to pyruvic acid. Their evidence indicated that it was pyruvic rather than lactic acid which represented the true end of anaerobic glycolysis.23 By 1942 Meyerhof was able to present

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what is essentially the modern view, and the Embden-Meyerhof pathway was established. 24 T h e glycogen or glucose was phosphorylated, and the various phosphate esters which had been identified were placed in their proper sequence in the scheme. The final ester, fructose diphosphate, appropriately called the Harden-Young ester, was split into two molecules of triose phosphate which, after dephosphorylation, led to pyruvic acid. T h e pathway was actually worked out in its details between 1933 and 1939, and the universality of its occurrence in all living organisms was then recognized. 25 It remained for Fritz Albert Lipmann (1899- ) to show the significance of the high-energy phosphate bond in ATP, and a further step in understanding bioenergetics had been taken. 26 T h e mechanism by which pyruvic acid was oxidized remained to be worked out. A number of investigators worked out what were actually portions of the cycle involved. In 1934 Albert SzentGyörgyi (1893- ) noted that respiration of muscle was increased by addition of succinic and fumaric acids and inhibited by malonic acid, which he correctly recognized as antagonistic to succinic acid. He suggested that succinate was a catalyst for a Thunberg type of hydrogen transport. 27 Further study convinced him of a close relation between fumaric and oxaloacetic acids, 28 a relation which was confirmed by Stare and Baumann. 2 9 Szent-Györgyi drew up a scheme for hydrogen transport by successive action of the three acids and established their participation experimentally.30 Since he believed that the acids functioned as hydrogen transporters in a manner analogous to the coenzymes in the transport of hydrogen from metabolites to oxygen, he was unable to see their proper function in pyruvate oxidation. At about the same time Carl Martius and Franz Knoop (1875-1946) demonstrated that citric acid could be formed from pyruvic acid, 31 and Martius worked out the sequence citric-aconitic-isocitric-oxalosuccinic acids. 32 Martius was an organic chemist more interested in the mechanisms of these reactions than in their biological significance and so did not connect these reactions with those studied by Szent-György. 33 The various studies were drawn together and correctly interpreted by Hans Krebs (1900) and W. A. Johnson. 3 4 Krebs had already come to the concept of a cyclic series of reactions

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as a result of his investigation of urea formation in the liver. 35 He had demonstrated that ornithine could pick up ammonia and carbon dioxide, leading to formation of arginine, which by loss of urea regenerated ornithine. He was therefore able, as he himself later said, 36 to picture a cycle which connected the results of Martius with those of Szent-Györgyi. In this cycle, oxaloacetic acid and pyruvic acid reacted to give citric acid, and after a long series of reactions in which water, carbon dioxide, and energy were given off at various stages, oxaloacetic acid was regenerated and could start the cycle again. This concept of a cyclic series of reactions has assumed an important place in recent biochemical thought. It now remained only to discover the mechanism of the combination of pyruvic and oxaloacetic acids to complete the aerobic cycle. This was accomplished by the discovery of coenzyme A by Lipmann. In 1945 he found an enzyme in the liver extracts which catalyzed the acetylation of sufänilamide. 37 Two years later he identified the vitamin pantothenic acid as part of the coenzyme molecule. 38 T h e function of the coenzyme was elucidated in 1951 by Feodor Lynen (1911- ) and his co-workers. 39 T h e complete pathway for the main oxidation of carbohydrates could now be visualized. One of the reasons for the success in working out the intermediary metabolism of the carbohydrates was the fact that it was possible to isolate many of the compounds which were involved in the metabolic pathway. In the case of the fats, this could not be done. However, it occurred to Franz Knoop that if he could label a molecule of fatty acid with something which could not be destroyed by the normal oxidative processes of the body, he might be able to isolate an intermediate product in the breakdown. Such an unoxidizable residue was the benzene ring. When a side chain was present on such a ring, the body could oxidize the chain only down to the ring itself, producing benzoic acid. This was eliminated from the body by conjugation with glycine to form hippuric acid, which was readily excreted in the urine and could easily be identified there. In 1905 Knoop reported the preparation of a number of fatty acids of varying chain length, but all with a benzene ring at the end. When he fed these to dogs he found

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that either hippuric acid or its next higher homolog, phenyl aceturic acid, were the only excretory products. When the side chain contained an even n u m b e r of carbon atoms, phenyl aceturic acid was excreted, while if the n u m b e r was odd, the product was hippuric acid. 40 From these facts he deduced that oxidation of fatty acids occurred with splitting off of two carbon atoms at a time f r o m the chain. This, the beta-oxidation theory, was the first step in elucidating the metabolic pathway of the fats, and f u r t h e r progress in this field was not m a d e until many years later in the century. T h e method which Knoop utilized, that of labeling a molecule with something which could be followed t h r o u g h a series of reactions, was to prove of the greatest value in subsequent biochemical studies. As new substances which could be used as labels became available, progress was m a d e in all branches of biochemistry. Major successes in labeling came with the discovery of isotopes. T h e heavy isotopes of light elements such as hydrogen, carbon, nitrogen, and oxygen were thus employed almost as soon as they were discovered. It was by utilization of heavy hydrogen that Rudolf Schoenheimer (1898-1941) was able to demonstrate that fats, instead of depositing and remaining in the fat depots until required for oxidation, were in a constant state of alteration and reaction. 4 1 This concept of the dynamic equilibrium of metabolites was soon extended f r o m fats to proteins and b r o u g h t about a marked change in the concept of metabolic equilibrium. In 1905 Otto Folin (1867-1934) had m a d e an extensive study of the conditions u n d e r which nitrogenous compounds a p p e a r e d in the urine. From this work he derived a theory which he expressed as follows: "It is clear that the metabolic processes resulting in the end products which tend to be constant in quantity a p p e a r to be indispensable for the continuation of life; or, to be more definite, those metabolic processes probably constitute an essential part of the activity which distinguishes living cells f r o m dead ones. I would therefore call the protein metabolism which tends to be constant, tissue metabolism or endogenous metabolism, a n d the other, the variable protein metabolism, I would call the exogenous or intermediate metabolism." 4 2 T h e idea that some nitrogenous com-

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pounds entered the tissues and remained there, only being lost in small amounts due to "wear and tear" while others were completely metabolized, dominated biochemical thinking for thirty years. After the work of Schoenheimer, however, it was realized that proteins also took part in a dynamic interplay. It became clear that the only body which reached the equilibrium state toward which so many bodily reactions tended was the dead one. T h e radioactive isotopes offered a still easier labeling device, and were taken u p by biochemists almost as soon as they were discovered. George de Hevesy (1885-1966) in 1923 used a natural radioactive isotope of lead to trace the movement of lead in plants, 43 and when artificial radioactive isotopes became available, he employed radioactive phosphorus in studying rat metabolism. 44 The use of such tracers has revolutionized many branches of biochemistry. Investigation of protein metabolism was much more difficult than was the case for the other classes of compounds. After Fischer had established these substances as polypeptides, numerous attempts were made to formulate chemical structures for proteins in terms of classical organic chemistry. 45 These attempts were not very successful, but much greater success in understanding protein behavior came from application of the methods of the newly developing science of physical chemistry. After the acceptance of the Arrhenius dissociation theory, attention turned to the ionic nature of amino acids and proteins. In 1894 Georg Bredig (1868-1944) in a footnote to a long paper on the stoichiometry of ionic mobility 46 noted that betaine must form an "inner salt" since in the same molecule there existed positve and negative charges which should neutralize each other. In 1897 F. W. Küster, working with methyl orange, called ions of this type zwitter ions. 47 Two years later Bredig accepted this term and pointed out that amino acids also formed zwitter ions. 48 Although it was generally accepted that such doubly charged ions could exist, most chemists felt that they could be found in solutions only in traces and that they played little part in chemical or physical behavior of amino acids. Their importance gradually became recognized, although the concept was not at first applied to the proteins themselves. In 1916 E. Q. Adams stated, "in solu-

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tion amino acids must exist as the 'inner salt' N + H 3 C H 2 C 0 2 V ' 4 9 but it was not until 1923 that Niels Bjerrum (1879-1958) finally established the significance of the zwitter ion formulation. 50 T h e delay in applying the zwitter ion theory to proteins seems all the more remarkable, since studies on the conductivity of these substances, beginning in 1899, had already indicated the amphoteric character of the proteins. In that year, William Bate Hardy (1864-1934) had studied the migration of egg white in an electrical field and had shown that "under the influence of a constant current the particles of proteid in a boiled solution of egg white move with the negative stream if the reaction of the fluid is alkaline; with the positive stream if the reaction is acid." 51 Continuing these studies, he concluded in the next year that "since one can take a hydrosol in which the particles are electronegative and, by the addition of free acid, decrease their negativities, and ultimately make them electropositive, it is clear that there exists some point at which the particles and the fluid in which they are immersed are iso-electric. This iso-electric point is found to be one of great importance. As it is neared, the stability of the hydrosol diminishes until, at the isoelectric point, it vanishes and coagulation or precipitation occurs, the one or the other according to whether the concentration of the proteid is high or low, and whether the iso-electric point is reached slowly or quickly, and with or without mechanical agitation." 52 T h e full significance of the isoelectric point was for a time obscured by the fact that Hardy, like most chemists of his day, felt that proteins were colloidal compounds which interacted with other compounds only by adsorptive forces on their surfaces. However, as he extended his studies he came to feel that true chemical reactions must also occur, an idea which he expressed in his long paper of 1905, 53 in which he stated "globulin therefore is an amphoteric substance and its acid function is much stronger than its basic function." He again stressed the importance of the isoelectric point in determining the direction of protein reactions. As long as no simple method for expressing hydrogen ion concentration existed, it was inconvenient to measure the exact value of the isoelectric points of different proteins. This difficulty was overcome in 1909 when S. P. L. Sörensen (1868-1939) proposed

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the use of an expression, which he denoted as/>H for the negative logarithm of the hydrogen ion concentration, and showed how to measure pW with a hydrogen electrode. 54 T h e universal acceptance of this concept greatly facilitated studies of protein chemistry. The idea that proteins reacted stoichiometrically with acids, bases, and salts as well as with organic compounds was finally fully established by further work of Sörensen after 1917 and by the extensive studies of Jacques Loeb (1859-1924), whose careful experiments showed the qualitative and quantitative reactions of proteins and the relation of such reactions to the p Η of the solutions. 55 There was still some hesitation in accepting the conclusions from these studies, but the work of E. J. Cohn (1892-1953) finally laid these doubts to rest. 56 A practical application of the conductivity studies on proteins was the development of the process of electrophoretic separation of proteins by methods largely dependent on the apparatus of Arne Tiselius (1902-1971). 57 This, together with the use of ultracentrifuge developed by T h e Svedberg (1884-1971), 58 made possible the preparation of many pure proteins. Improved methods of separation of simpler compounds, such as the individual amino acids, were also achieved during this period by discovery of better methods of chromatography. Chromatography was originally used by Michael Tswett (1872-1920) for separation of plant pigments. 59 Its use was later extended to many other types of compounds. Mid-twentieth century discovery of methods for determining the sequence of amino acids in proteins and then for the synthesis of even very complex substances produced results which had seemed impossible in earlier years. Thus, Frederick Sanger (1918- ) succeeded in working out the complete structure of the molecule of beef insulin, which he showed to consist of two polypeptide chains linked by disulfide bonds. He broke the disulfide links by mild oxidation, determined the order in which the amino acids were linked in each chain, and showed where the cross links occurred. 60 Thus insulin was shown to be a definite chemical molecule for which a complete structural formula could be written.

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Following Sanger's pioneer work other investigators determined complete amino acid sequences for hundreds of proteins, and the fact that proteins are true chemical molecules was definitely established. X-ray diffraction studies of protein crystals, beginning with the work of J. C. Kendrew (1917) on myog61 62 lobin and M. F. Perutz (1914) on hemoglobin, revealed the three-dimensional architecture of protein molecules in detail and led to a far deeper understanding of the structure and action of enzymes. T h e chemistry of the proteins themselves was thus greatly advanced in the twentieth century, but it remained clear that the oxidation of these substances could be explained only in terms of the reactions of the individual amino acids. Here the problem was much the same as in the case of the fats. Once the nitrogen had been split off, no intermediate products were known. T h e early work of A. E. Garrod (1857-1936) had shown that in certain rare cases of "inborn errors of metabolism" some intermediates in the oxidation of a few amino acids were excreted, 63 but the significance of this work was not appreciated until genetic studies showed that such mutations were commoner than had been thought and could be artificially induced in experimental organisms. By the middle of the century the utilization of these techniques, as well as the understanding of the central position of pyruvic acid, or rather of acetyl coenzyme A derived from its oxidative decarboxylation, permitted visualization of the individual metabolic pathways of the amino acids. T h e intermediary metabolism of the carbohydrates, fats, and amino acids was shown to lead ultimately to the same simple substances. T h e demonstration of the interrelationships of all bodily constituents has been one of the triumphs of modern biochemistry.

18 Vitamins

The existence of specific diseases now ascribed to lack of essential food elements had been known to physicians from very early times, and empirical methods of treatment had sometimes been developed. Mention has been made of the old Chinese use of liver to cure night blindness and the use by Hawkins of oranges and lemons to cure scurvy in 1593. T h e concept of a dietary deficiency was expressed in 1841 by Budd, who believed the curative action of antiscorbutic foods was due to "an essential element, which, it is hardly too sanguine to state, will be discovered by organic chemistry or the experiments of physiologists in a not far distant future." 1 Systematic study of various types of diet began in the latter part of the nineteenth century. It soon became apparent from these that generalizations such as the isodynamic law could not explain all the results obtained by feeding synthetic diets which supposedly contained all needed elements. However, the concept of a deficiency disease was difficult to accept. The success of the new science of bacteriology in pointing to specific infective agents as the cause of diseases led investigators to seek a positive reason rather than a negative lack to explain the etiology of a pathologi-

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cal state. This was particularly true of men closely associated with the medical profession. Chemists in agricultural stations were less affected by the germ theory, and so it happened that much vitamin reasearch was carried on in such institutions. 2 Even when the possibility of deficiency states was recognized, the confusion of symptoms produced by them and the multiplicity of substances involved made understanding of the causative factors difficult. T h e earliest scientific observations on vitamin deficiencies were made almost accidentally. T h e first important contribution came from Nikolai Ivanovich Lunin (1854-1937) in 1881.3 He was testing the effect of certain salts and salt mixtures in the diet of mice. Animals on his ash-free diet died quickly when the mixture was fed with distilled water, but when a little milk was added, they survived and remained healthy. Lunin offered no real explanation for this fact. At about the same time, Kanehiro Takaki (1849-1915), who had been trained in England and who became director general of the medical department of the Japanese navy, became concerned at the prevalence of "kakke" (beri beri) in the navy. T h e disease had become common throughout the orient when, some years earlier, the unpolished rice which had been a staple of the diet was replaced by polished rice. Takaki believed the disease was due to a deficiency of nitrogen and an excess of carbon in the diet. He introduced meat and condensed milk to the sailors' diet to correct this imbalance. T h e disease almost disappeared from the navy.4 This was actually a well-controlled experiment, for the civilian population remained on its usual diet and continued to suffer from the disease. However, the incorrect theory behind Takaki's alteration of the diet and the preoccupation of most physicians with the germ theory of disease obscured the significance of the work. T h e studies of Lunin and Takaki indicate the two lines of research which were followed in later years as the vitamin concept was gradually developed. On the one hand, a number of investigators tested synthetic diets which proved inadequate in some respect, usually a failure to promote growth in young animals. Addition of specific supplements was then shown to cause normal development. On the other hand, some groups of investigators

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studied the specific pathological conditions and traced their production and cure in experimental animals. Lunin's method was followed by a number of workers in the 1890s. Typical of their results and among the best interpretations were those of C. A. Pekelharing (1848-1922) in 1905. He summarized his work along these lines as follows, "My intention is only to point out that there is still an unknown substance in milk, which, even in very small quantities, is of paramount importance to nutrition. If this substance is absent, the organism loses the power properly to assimilate the well known principal parts of food, the appetite is lost, and with apparent abundance the animal dies of want. Undoubtedly this substance not only occurs in milk but in all sorts of foodstuffs, both of vegetable and animal origin." 5 A similar conclusion was reached by Thomas B. Osborne (1859-1929) and Lafayette B. Mendel (1872-1935) in 1911.6 A different approach by Wilhelm Stepp in 1909 also showed the value of some constituents of milk. 7 He was attempting to determine whether animals could themselves synthesize fats, or whether these could come only from plant sources. He fed a bread made with milk and found it was adequate for animal survival. He then extracted the bread with alcohol and ether. When fed only the extracted bread, the animals died, but when the alcohol-ether extract was also fed, they survived. He concluded that animals cannot live without lipoids, especially those found in milk, but he had no idea which lipoids were essential. The paper which brought together all the previous studies of this type and once and for all established the importance of accessory food factors was published in 1912 by F Gowland Hopkins. 8 The care and completeness with which his experiments were carried out and his leading position in the biochemical field made the paper a classic. He pointed out that diets consisting of mixtures of pure proteins, fats, carbohydrates, and salts were adequate only when a little milk was added, and he noted that "a substance or substances present in normal foodstuffs (e. g. milk) can, when added to the dietary in astonishingly small amounts, secure the utilization for growth of the protein and energy contained in such artificial mixtures." He also said, "It is possible that what is absent from artificial diets and supplied in

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such addenda as milk and tissue extracts is of the nature of an organic complex (or complexes) which the animal body cannot synthesize. But the amount which seems sufficient to secure growth is so small that a catalytic or stimulative function seems more likely." T h e first really significant studies of the deficiency diseases themselves were those carried out in Java by Christiaan Eijkman (1858-1930). His results were first published in Dutch in 1890, but they were brought to the attention of the medical world by his German paper of 1897.9 In this he reported that hens fed the leftover portions of cooked polished rice from a hospital kitchen developed a disease resembling human beri beri. This could be prevented or cured by feeding a diet of raw unpolished rice or of fresh meat. He at first believed the disease was due to an infection, but he could not transmit it from one bird to another, nor could he find a microbe or more highly organized parasite. He therefore thought that the condition must be caused by a toxic substance, a nerve poison, in the polished rice which was neutralized by a "protective substance" in the polishings. According to Eijkman, "It further follows that the substance must be a normal constituent of the animal organism whose absence causes illness." T h e animal forms of beri beri came to be called polyneuritis. Eijkman's work in Java was continued in 1901 by Gerrit Grijns (1865-1944). He confirmed the effect of polished rice but proposed the theory that beri beri occurred because the diet "lacked certain substances of importance in the metabolism of the nervous system." 10 By 1906 Eijkman, who had continued his experiments in Holland, was ready to accept this view. He said, "Grijn thinks that in various natural foods a portion exists which cannot be missing without damage to the peripheral nervous system and that some foods are very poor in this." 11 He tried to isolate the substance but was able to conclude only that it was present in a phosphate-rich fraction of an extract. Later more elaborate efforts at isolation of the antineuritic factor were made by the Polish investigator, Casimir Funk (18841967), working in England. He used large quantities of yeast or rice polishings and extracted them with alcohol. He accounted for

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the phosphate noted by Eijkman by obtaining considerable quantities of choline, which, however, had no biological activity.12 In 1914 Jack Cecil Drummond (1891-1952) and Funk isolated comparatively large amounts of choline, betaine, and, interestingly enough, nicotinic acid from their rice polishings. Since none of these cured beri beri, they did not consider their findings significant, thus overlooking the vitamin nature of nicotinic acid. They assumed that the curative substance was decomposed during fractionation. 13 Most investigators at this period assumed that there was only one factor whose lack produced a disease. It was with this in mind that the Norwegian workers Axel Hoist (1861-1931) and Theodore Frölich (1871-1953) in 1907 investigated "ship beri beri," a disease which affected Norwegian sailors on long voyages. Hoist studied the disease in sailors and noted that when fresh food was added to their diets, they quickly recovered. 14 He doubted that the disease was identical with the tropical beri beri of Java and suggested that perhaps it was a form of scurvy. He therefore undertook a laboratory study of the condition with Frölich and fortunately used guinea pigs as his experimental animals, 15 since rats would not have shown the disease. Hoist and Frölich considered and rejected the idea that the condition came from an infection or from spoiled food. They concluded that it came from a "one sided diet" consisting of groats and bread. Cabbage and fresh potatoes were curative, dried potatoes or cooked cabbage were not. T h e disease was "macro- as well as microscopically" identical with human scurvy, and thus another deficiency disease was definitely identified. Ship beri beri was apparently a combination of beri beri and scurvy. The entire subject of deficiency diseases was placed on a firm foundation by Casimir Funk in 1912.16 He gave an extensive review of the literature and for the first time used the name deficiency diseases. He pointed out that beri beri, avian polyneuritis, epidemic dropsy, scurvy in all its forms, and ship beri beri all belonged in this class. His own experience with attempts to isolate the anti-beri beri factor led him to believe that the curative substance was an organic nitrogenous base, that is, an amine, and that it was vital to life. He therefore proposed the name

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"vitamine" for the substance: "It is now known that all these diseases, with the exception of pellagra, can be prevented and cured by the addition of certain protective substances; the deficient substances, which are of the n a t u r e of organic bases, we will call 'vitamines.' and we will speak of a beri-beri or scurvy vitamine, which means a substance preventing the special disease." With great foresight, he said of pellagra, then thought to be d u e to an infection, that it was "included provisionally, owing to its similarity in some respects to the other diseases mentioned." T h e variety of deficiency diseases itself suggested that there might be m o r e than one curative agent involved, and evidence that this was the case was not long in appearing. In 1913 Elmer V e r n e r McCollum (1879-1967) and Marguerite Davis noted that rats required some ether-soluble material for growth. 1 7 In the same year Osborne and Mendel showed that animals fed on protein-free milk failed to grow but when butter was added to the diet, growth was resumed. T h e growth-promoting factor was f o u n d in the fat fraction of the butter, which contained no nitrogen. 1 8 Two years later McCollum and Davis clearly distinguished the accessory water-soluble factor which prevented beri beri f r o m the substance in butter fat which produced growth. 1 9 T h e y s u m m e d u p their conclusions: "We must therefore conclude with Stepp, Hopkins, Funk, and others f r o m the extensive data now available that certain at present unidentified substances aside f r o m protein, carbohydrates, fats, and salts are indispensable f o r growth or prolonged maintenance, and f u r t h e r more that there is a class of such accessories soluble in fats and a n o t h e r soluble in water a n d alcohol." 20 In the next year McCollum suggested a revision in nomenclature. Since not all the factors contained nitrogen, he rejected Funk's term vitamine, and he objected equally to the Hopkins term accessory factor, since it implied that these substances were less important constituents of the diet. H e proposed calling the curative substances "fat soluble A" and "water soluble B." 21 Shortly afterward the antiscorbutic factor was called water-soluble C. T h e final standardization of the nomenclature was proposed by D r u m m o n d in 1920. H e noted that McCollum's system was awkward and that Funk's term had been so widely adopted that

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it was not advisable to give it up. T h e factors were not amines, and so he suggested dropping the final "e" of the Funk name and combining the systems to refer simply to vitamin A, vitamin B, and so on. 22 The simplicity of this system made it at once acceptable, and it has remained standard ever since, even when individual names have been given to the separate vitamins. As the vitamins were further studied, it became evident that substances considered individual could be separated into new groups. Fat-soluble A was at first assumed to have two functions: prevention of the eye disease xerophthalmia, and control of calcium deposition in the bone, disturbance of which resulted in rickets. In 1922 McCollum and his co-workers showed that if cod liver oil, which possessed both properties, was oxidized for 12 to 20 hours, it lost its antixerophthalmic property but still could prevent rickets. Thus there was "a fourth vitamin whose specific property, as far as we can tell at present, is to regulate the metabolism of bones." 23 This discovery raised a new problem. It was a well-known fact that rickets could be prevented by exposure of the body to ultraviolet radiation. How could a physical treatment such as this be reconciled with a chemical substance which had the same action? A partial explanation became possible when Harry Steenbock (1886-1967) showed that irradiation of a rat ration by ultraviolet light rendered it antirachitic. 24 Almost simultaneously Alfred Hess (1875-1933) showed that such irradiation conferred antirachitic power on cottonseed and linseed oil and on green lettuce. 25 Hess remarked, "An antirachitic factor therefore has been produced in vitro and outside the living organism. The irradiated oils were able to store this factor for a considerable period." Steenbock was led to comment that "it suggests itself that, in ultimate analysis, both light and the antirachitic vitamin may represent the same antirachitic agent—possibly a form of radiant energy." In this way he attempted to solve the problem raised by the new discovery. Since no specific chemical compound had been isolated u p to this time which could be claimed to be a vitamin, his suggestion was not impossible, though it was certainly speculative. T h e chemical nature of the vitamin was becoming clear, however. Hess and Weinstock in 1925 irradiated a supposedly pure

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sample of cholesterol and f o u n d that it became active. 26 Further purification of the cholesterol showed that not it but a contaminant was activated, 27 and finally Hess and Adolf Windaus (18761959) demonstrated that the substance activated was ergosterol. 2 8 T h e activated substance was naturally called vitamin D. For seven years it was accepted that ergosterol was the only substance activated by light, a l t h o u g h t h e p r o p e r t i e s of the activated ergosterol did not entirely agree with those of the vitamin f r o m cod liver oil. At last Waddell in 1934 showed that the impurity in cholesterol was not always ergosterol. H e noted that his results "indicate that the provitamin present in cholesterol is not identical with ergosterol, a finding which is in direct conflict with a f u n d a mental concept on which much of the m o d e r n theory of vitamin D activity is based." 2 9 In the next year the Windaus g r o u p synthesized 7-dehydrocholesterol and definitely stated, "On the basis of o u r researches there is no more doubt that a n u m b e r of sterols which are distinguished f r o m each.ojther by the length of the side chain or the n u m b e r of double bonds can become antirachitic if only they have the characteristic conjugated double bonds in Ring β »30 chemistry of the D vitamins was soon clarified. J u s t as the fat-soluble vitamins had been shown to consist of two d i f f e r e n t substances, the Β vitamins t u r n e d out to be mixtures also. In 1926 Joseph Goldberger (1874-1929), after a prolonged investigation, proved that pellagra was actually a deficiency disease 31 as Funk had suspected. H e called the vitamin which was involved the P. P. (pellegra-preventing) factor. Chick and Roscoe 32 showed that it was f o u n d in the same sources as the antineuritic factor a n d stated that McCollum's water-soluble Β was actually a mixture of Eijkman's anti-beri beri factor and Goldberger's P. P. factor. For a time the n a m e vitamin G was given to the P. P. factor by some authors, while others p r e f e r r e d to distinguish the d i f f e r e n t factors as vitamins Bi, B2, and so on. Although for a time there was great confusion as to the n a t u r e of the various factors and the symptoms their deficiencies produced, it was generally accepted by the late I920's that the n a m e vitamin Β covered at least two substances, the heat-labile antineuritic factor, which was now called Bi, and a heat-stable factor called B2. T h e complexity of B2 was gradually realized, and

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during the 1930s it was resolved into riboflavin, 33 for which the term B2 was reserved as soon as it was realized that it differed from the P. P. factor, 34 pyridoxin (Be), first called adermin, 3 5 and a series of substances named as soon as discovered and hence not using the numerical Β nomenclature. One of the most important of these later discoveries was the identification of Goldberger's P. P. factor as nicotinic acid, 36 which Funk had isolated from rice polishings but had not regarded as a vitamin because it did not prevent beri beri. As indicated in Chapter 17, a beginning was made at this time in understanding the function of some of the Β vitamins, when they were found as parts of various coenzyme molecules. Vitamin E, the so-called fertility vitamin, was discovered in 1922 by Herbert M. Evans (1882-1971) and K. S. Bishop, 37 and vitamin Κ by Henrik Dam (1895) in 1935.38 This completed the list of fat-soluble vitamins. Nearly all the work of sorting out the various vitamins and determining their physiological and many of their chemical properties had been carried out on concentrates from various natural sources, but up to about 1930 no one had isolated a pure chemical compound which could be proved to be a vitamin. The first active substances isolated turned out to be, not vitamins, but provitamins, a name which denotes a new concept in the field. As early as 1919 Steenbock had pointed out that most yellow vegetables had vitamin A activity, while colorless ones did not. He suggested that the vitamin was "a yellow pigment or closely related compound." He even mentioned carotene as a possibility for consideration. 39 However, in the same year Drummond tested a large number of fatty substances, including carotene, and said that none had any vitamin activity.40 Considerable controversy ensued over the next few years, but in 1925 Drummond apparently settled the matter. 41 He found complete inactivity in a pure carotene preparation. It was later shown that the diets he used lacked not only vitamin A but also vitamin D, and so growth had not occurred when only A active material was fed. In 1928 Hans von Euler (1873-1964) finally proved in Stockholm that carotene actually could replace vitamin A in the diet, a fact which was thereafter generally accepted. 42 The problem of the nature of vitamin A now became involved with the investigation of the structure of the carotenoid pigments,

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yellow or red coloring matters of many plants. Carotene, the pigment of carrots, had been under investigation for nearly a hundred years. In 1930 and 1931 Paul Karrer (1889-1971) in Zurich finally established the structure of this complex substance. 43 It was obvious that the vitamin in cod liver oil was not carotene itself, in spite of the latter's physiological activity, since the oil was not highly colored, as was carotene. Karrer now took up the study of the structure of the vitamin. He was able to secure the liver oils of certain Japanese fish which were 200 to 2000 times as active as those of the cod. From these he obtained very highly concentrated preparations of the vitamin, and he was able to determine its structure even before it had been isolated. 44 The molecule of the vitamin was just half the molecule of /3-carotene. Thus carotene was a plant substance which the animal body could convert into the true vitamin. It was therefore called a provitamin, and, naturally enough, the precursors of vitamin D were also called provitamins. T h e provitamins had been shown to be definite chemical compounds, but the vitamins themselves still eluded isolation. Their discovery was now at hand, however. In 1928 Albert SzentGyörgyi was investigating oxidizing-reducing substances in living organisms. He isolated a substance from the adrenal cortex which, he said, was "a highly reactive isomer of glycuronic acid, so that the substance is hexuronic acid." 45 Subsequently he isolated much greater amounts of the substance from Hungarian paprika, 46 and with W. N. Haworth (1883-1950), who had been working on the structure of sugars, he became convinced that his hexuronic acid was actually vitamin C. He and Haworth wrote: "In view of the fact that 1) hexuronic acid is the name of a class of substances rather than that of one individual compound and that 2) the material described as hexuronic acid isolated from the adrenal cortex and now from paprika contains a molecule of water less than is required for a hexuronic acid, we wish to ascribe the name ascorbic acid to the crystalline substance CeHeOe which has been the subject of earlier communications from our laboratories." 47 Almost at once ascorbic acid was synthesized independently by Tadeus Reichstein (1897) in Zurich 48 and by Haworth and co-workers in England. 49 T h e demonstration that the natural vitamin and synthetic ascorbic acid had identical chemical and

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physiological properties proved that at last a vitamin had been obtained as a pure chemical compound. 5 0 Szent-Györgyi was able to startle the chemical world by delivering a lecture on vitamin C and at the end remarking, "I thought you might like to see a vitamin." He then produced a bottle containing several kilograms of ascorbic acid. T o chemists accustomed to think of vitamins as substances obtainable, if at all, in only the most minute amounts, this was a surprising experience. The isolation and synthesis of most of the other vitamins followed quickly, and vitaminology became a standard branch of biochemistry.

19 Hormones

T h e discovery of vitamins introduced a new concept into biochemistry and physiology. Similarly the gradual development of the idea of hormones also introduced a new concept. 1 Strictly speaking, the idea of a specific substance or substances elaborated by the body and capable of altering the body state was very ancient. T h e Aristotelian and Galenic theory of the balance of humors embodied it. After the Renaissance, however, the humoral theory was abandoned, not only because it was Galenic and hence outmoded but also because of the growing knowledge of nerves and nerve conduction. Thus it came about, as F. Gowland Hopkins remarked, that "up to near the end of the last century nearly every expert looked to the influence of the nervous system alone as concerned with the co-ordination of functions in the body; the conception of chemical regulation and co-ordination had achieved no place in the minds of the majority." 2 Just as the belief in the germ theory made it difficult to accept the idea of a deficiency disease, so the concept of nervous control of the body made it difficult to accept the idea of chemical control. However the idea of some specific governing substance coming from specific organs or tissues never completely died out. Thus,

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in 1775 the French physician Theophile de Bordeu (1722-1776) suggested that each organ in the body gave off "emanations." He called particular attention to the emanations from testicular and ovarian tissues, but he believed that every organ gave off an essential substance which was required by the body as a whole. During the eighteenth and early nineteenth century a number of such vague suggestions were made, but these had little influence on physiological thought. 3 Beginning in the middle of the nineteen' ! century evidence steadily accumulated that a chemical control ictually existed and that a number of clinical conditions could be directly associated with defects in certain ductless glands, many of which had previously appeared functionless. By the end of the century so much information had been acquired that generalization of the concept of hormones could be made. The first experimental demonstration of the effect of a specific ductless gland was made in 1849 by A. A. Berthold (1803-1861). He transplanted the testes of a cock and found that they functioned in the new location to maintain comb growth, a secondary male characteristic in these birds. Since the transplanted glands no longer had their normal nerve connections, he suggested that they acted on the blood, and thus through the blood on the general organism. 4 Therefore the hormone concept was indicated even at this early stage, but the work was generally overlooked at the time of its publication. In 1853 the term "internal secretion" was coined by Claude Bernard. 5 He applied it to the process which he had discovered in which the liver formed glucose and poured it out into the blood. Although this use of the term is more general than is now accepted, it was taken up, especially by French physiologists, and gradually made more precise as the hormone concept developed. Diseases now known to be due to endocrine malfunction, especially those with dramatic symptoms, were described with increasing frequency at this period. In 1855 Thomas Addison published the description of the disease which bears his name. He thought the symptoms might be due to an effect of diseased adrenal glands on local nerve centers throughout the gland. 6 In the following year Charles Edouard Brown-Sequard (1817-1894) removed the adrenals from experimental animals and found that

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the subject died. He believed the glands removed a toxic substance from the blood. 7 The theory of a detoxifying action was later extended to the action of other ductless glands. In 1873 W. W. Gull gave the name myxoedema to a clinical condition which had long been known to exist and which had been related to the state called cretinism. T. Kocher of Berne in 1883 reported on a large number of cases of this disease. A discussion of myxoedema took place at a meeting of the Clinical Society of London in 'November 1883 at which Felix Semon called attention to Kocheß s work and directly associated the disease with loss of thyroid function. 8 Experimental evidence for this conclusion followed in the next year. Victor Horsley (1857-1916) removed the thyroid gland from monkeys and observed that a cretinous condition resulted. 9 Moritz Schiff (1823-1896) pointed out that he had performed a similar experiment in 1858, though he had not drawn a general conclusion from it. He now remarked that the analogy of thyroid, spleen, and pancreas suggested "that these glands prepared a substance which played the part of an essential mediator within the blood vessels for nourishing the nerve centers." 10 Direct evidence for the presence of an essential substance was obtained by George Murray in 1891 when he fed sheep thyroid to a patient suffering from myxedema and found marked improvement in the symptoms. 11 T h e apparently obvious suggestion from this work was that since too little of the glandular substance produced a definite set of symptoms, too much of it should produce an opposite effect. This conclusion was reached only slowly. L. Rehn in 1884 suggested that Graves' disease might be due to an enlarged thyroid, 12 and Greenfield in 1893 associated hyperplasia of the thyroid with "exaggerated function" rather than with a disease of the nervous system as most clinicians had done. 1 3 T h e idea was not strongly supported until 1898, when A. von Notthafft reported the case of a patient who took a thousand tablets of thyroid gland substance over a period of five weeks. Typical symptoms of Graves' disease appeared and gradually disappeared when taking of the tablets was discontinued. 14 Brown-Sequard, always an enthusiast, startled the medical world in 1889 by claiming that by injecting himself at the age of 72 with mammalian testicular extracts he had brought about a

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Development of Biochemical Concepts

remarkable rejuvenation. 15 Although it is generally agreed that the effects he claimed were largely psychological, h£ did much to call attention to the importance of glandular extracts. In 1891 he and d'Arsonval said: "We believe that all tissues, glandular or not, give something special to the blood, that all acts of nutrition are accompanied by an internal secretion." They suggested that extracts of each tissue could be used for a specific therapeutic purpose as needed. 1 6 This doctrine represents a revival of the views of de Bordeu. Another long-known disease was also shown at about this time to be due to a lack in a specific gland. In 1889 Oscar Minkowski (1858-1931) and J. von Mering (1849-1908) at Strasbourg were attempting to discover the function of the pancreas. Minkowski suggested a test for this by removing the organ. With von Mering's assistance, the operation was performed on a dog. Later Minkowski observed the dog urinating frequently. This was known to be a smyptom of diabetes, and he therefore almost routinely tested the urine for sugar. T o his surprise he found a high content. This observation led to the publication of their fundamental paper in this field.17 Although von Mering's name appeared first in the title, there seems little doubt that chief credit for the discovery belongs to Minkowski. 18 It was suggested at the time that the glycosuria was due to damage to the nerve centers during the operation, and idea reminiscent of the proposal of Addison that his disease of the adrenals might be due to a similar cause. This suggestion was shown to be false by the same type of evidence Berthold had used in 1849. Hedon in 1893 showed that when a piece of pancreatic tissue was transplanted to a new location, no diabetes resulted. 19 Another function of the adrenal gland was observed for the first time by George Oliver (1841-1915). He was measuring the size of the peripheral arteries, using his son as the subject. He gave by mouth an extract of adrenal glands and believed he saw a constriction of radial artery. He took his extract to the physiologist Edward Albert Schäfer (1850-1935) in London. (Schäfer is better known by the compound name SharpeySchäfer, which he later assumed). At the moment Schäfer was carrying on an experiment on a dog whose blood pressure he was

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measuring. When the experiment was complete, Oliver asked the physiologist to inject some of his adrenal extract. To the amazement of both men, a very great increase in blood pressure occurred. 20 They continued the investigation and were able to report in 1894 the effects of the extract on blood pressure, arterial contraction, and heart stimulation. 21 In the next year they confirmed these results and showed that the active principle was present in the medulla of the gland only. 22 Their long report of 1895 gave the details of their work. 23 Since adrenaline (epinephrine) is chemically the simplest hormone, it is not surprising that it was also the first to be isolated in the crystalline state. This was accomplished independently in 1901 by Jokichi Takamine (1854-1922) 24 and Thomas Bell Aldrich. 25 Its synthesis followed, carried out by Friedrich Stolz in 190 4 26 and by H. D. Dakin in 1905.27 T h e identity of a hormone as a chemical individual was thus established long before a similar result was obtained for vitamins. I h f a c t , it was established even before the concept of hormones had been clarified and the name hormone proposed. The concept of hormones was finally placed on a firm foundation by the work of Bayliss and Starling on secretin. In 1902 William Maddock Bayliss (1860-1924) and Ernest Henry Starling (1866-1927) published their classic study on the mechanism of pancreatic secretion. 28 They showed that the production of pancreatic juice occurred when acid chyme entered the duodenum, and that this secretion did not depend on a nervous reflex, since it took place when all nervous connections to the intestine had been destroyed. They said, "The contact of the acid with the epithelial cells of the duodenum causes in them the production of a body (secretin) which is absorbed from the cells by the blood current, and is carried to the pancreas, where it acts as a specific stimulus to the pancreatic cells, exciting a secretion of pancreatic juice proportional to the amount of secretin present." T h e discovery of secretin and its action was only one of a series of similar discoveries, but from it resulted the fundamental concept of the hormones, as well as the name. These were proposed in the Croonian Lectures which Starling delivered in 1905. In the first of these lectures, entitled "The Chemical Control of the

228

Development of Biochemical Concepts

Functions of the Body," 2 9 h e pointed out that originally the responses of unicellular organisms were to chemical substances. Even a f t e r the nervous system had developed in higher animals "a study of the p h e n o m e n a of even the highest animals shows that t h e development of the quick nervous adaptations involves n o abrogation of the other more primitive class of reactions—i.e., the chemical ones." H e discussed two classes of pharmacological substances: those which gave rise to antibodies a n d those which did not. H e went on to say, " T o which of these two groups of bodies must we assign the chemical messengers which, speeding f r o m cell to cell along the blood stream, may coordinate the activities and growth of diff e r e n t parts of the body? T h e specific character of the greater part of the toxins which are known to us (I need only instance such toxins as those of tetanus a n d diptheria) would suggest that the substances p r o d u c e d for effecting the correlation of organs within the body t h r o u g h the intermediation of the blood stream, might also belong to this class, since h e r e also the specificity of action must be a distinguishing characteristic. T h e s e chemical messengers, however, or'hormones'(fromcPMaw, I excite or arouse), as we might call them, have to be carried f r o m the organ where they are p r o d u c e d to t h e organ which they affect by means of the blood stream a n d the continually recurring physiological needs of the organism must d e t e r m i n e their repeated production and circulation t h r o u g h the body." H e showed that they did not give rise to antibodies and so said, "We are t h e r e f o r e forced to the conclusion that if the processes of coordination of activities a m o n g the organs of the body are carried out u n d e r physiological conditions to any large extent by chemical means—i.e., by the dispatch of chemical messengers along t h e blood stream—these emissary substances must belong to Ehrlich's second o r d e r of substances acting on the body, a n d must, in fact, fall into the same category as the d r u g s of o u r Pharmacopoeia." It was recognized almost immediately that the products of the o t h e r ductless glands could be classified like secretin, a n d the n a m e h o r m o n e was generally accepted for these chemical messengers. T h e problem of the isolation a n d synthesis of most of t h e m

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remained. Those whose chemical structure was relatively simple were soon characterized. Thyroxine was isolated by Kendall on Christmas day, 1914,30 and was synthesized by Harington and Barger in 1927. 31 The isolation and structural determination of the other hormones awaited the development of suitable chemical and physical methods adapted to their particular structures. T h e discovery by Swingle and Pfiffner in 193032 that a fat solvent could be used in the preparation of an active principle from the adrenal cortex opened the way to isolation of the steroid hormones of the adrenal cortex and the gonads. It is interesting to note that, just as the structure of vitamin A was determined before it had been isolated, but after the structure of its parent, carotene, had been worked out, so Butenandt was able to determine the structure of the male sex hormone androsterone using only 25 milligrams of the crystalline material because the structure of its parent substance, cholesterol, had been determined. 3 3 T h e isolation of pure protein hormones took longer, because suitable methods of protein chemistry had to be developed, but isolation and even synthesis of some of these followed by mid-century. Much of the early work on hormones was concerned with the action of the secretions of individual glands. However, in 1907 Claude and Gougerot 34 described a clinical syndrome resulting from simultaneous failure of several glands. They referred to this as a "pluri-glandular insufficiency." In the next year Eppinger, Falta, and Rudinger studied the effect of extirpation of two glands at a time and also the effect of extirpation of one gland on the function of another. 35 Work of this type on the interrelation of the glands was clarified, and the concept of a dominant gland, the pituitary, was explained by Harvey Cushing (1869-1939) in 1912. He wrote: "There is probably a fairly definite clinical symptom-complex for a primary involvement of each of the ductless glands, whether the involvement is of such a character as to excite, on the one hand, an excessive secretion or, on the other, to diminish functional activity. In some cases, however, the symptomatology may be so confused that it is impossible to tell which of the individual glands is actually the primary seat of disease. We may in time be able

?30

Development of Biochemical Concepts

to determine this by the slow therapeutic tests of feeding the active principle of one gland after another; or a more expeditious method may be supplied by the immediate reactions which follow the subcutaneous or intravenous injections of the various extracts. In brief, the term "polyglandular syndrome" indicates merely that secondary functional alterations in members of the ductless gland series occur whenever the activity of one of the glands becomes primarily deranged. Further, the term as here employed is restricted to those cases in which it is difficult to tell which of the structures is primarily at fault. 36 More recent work on the hormones has only served to emphasize the interrelations of these substances, and still more recently to tie together the interactions of the hormones and the nervous system.

20 Afterword

In the beginning of this book biochemical concepts were defined as those which explained the processes of the body in terms of material substances. For centuries these concepts were expressed in terms of more or less hypothetical substances. As increasing numbers of specific compounds were discovered, the concepts themselves became more specific. By the nineteenth century many hundreds of biologically significant substances were known, and more were discovered each decade. Individual physiologists and physiological chemists could follow the track of only a few of these compounds at a time. Therefore the pages of the journals at this period were filled with long accounts of apparently unrelated facts. T h e twentieth century saw the beginning of attempts to draw these unrelated facts together in a series of metabolic pathways. The interconversions of carbohydrates, proteins, and fats, the mechanisms and function of enzymes and coenzymes, and their involvement with vitamins all combined to make biochemistry an increasingly unified science. T h e culmination of this unifying tendency was the discovery of the function of the nucleoproteins in the cell.

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Development of Biochemical Concepts

Although much of the information needed for an understanding of such function had been available for some time, incorrect interpretations prevented the integration of biological and chemical aspects. Then in 1944 Avery, MacLeod, and McCarty 1 demonstrated that a chemically isolated fraction containing a deoxyribonucleic acid could bring about a permanent, inheritable cell alteration in a type of pneumococcus. This indicated a genetic role for a chemical agent and pointed to the nucleic acids as the responsible substances. It was still difficult to picture a chemical mechanism for two reasons. First, the very large size of the nucleic acid molecule was not recognized. As a result of the progress of colloid chemistry in the early years of the century, chemists had tended to think of large particles as mere aggregations of substances with relatively low molecular weights. A change in this concept began when Staudinger 2 introduced the term "macromolecule" and showed that macromolecules were actual chemical compounds of enormous size. T h e concept was slowly accepted by chemists. Olby 3 has called this realization the true origin of molecular biology. T h e other necessary step in realizing that the nucleic acids could act as code bearers came when Chargaff 4 showed that the tetranucleotide hypothesis of Levene was not valid, that there was a variable distribution of bases in a very large molecule, and that there was a relationship between certain purine-pyrimidine pairs. A rapid reorientation of thinking followed, leading to the double helix theory of Watson and Crick, 5 which at once provided a biochemical mechanism to explain the facts of genetic inheritance. Two helical strands of deoxyribonucleic acid (DNA), held together by hydrogen bonds between the pairs of nitrogenous bases, were the essential constituents of the gene. They could separate during cell division, and each in a daughter cell could regenerate its complement. The original double helix was thus reformed in each new cell, that is, the same gene again existed. Geneticists had accepted the idea that each gene produced an individual enzyme. The double helix theory accounted for this fact also. Each triplet of nitrogenous bases in the DNA corresponded to a single amino acid, and the sequence of triplets formed a code for protein synthesis. The code was transferred

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from the DNA to a strand of ribonucleic acid (RNA), which served as a messenger to transfer the code to the ribosomes of the cytoplasm where actual protein synthesis occurred. T h e enzymes thus formed catalyzed almost all bodily reactions. T h e steps in the development of these ideas have been described by Chargaff, 6 and the personal side of the story has been told by Watson. 7 More recent developments are discussed by Watson 8 and by Stent. 9 T h e theories of the roles of DNA and RNA have brought about an integration of genetics and biochemistry which is only a higher step in the integration of biochemical concepts of the interrelation of metabolic pathways. In the last third of the twentieth century it has become clear that the fundamental concepts of biochemistry, the outgrowth of over two thousand years of speculation and experiment, lie and will continue to lie at the basis of all the sciences of life.

Notes

Index

Notes

1 The Earliest Concepts 1. Henry E. Sigerist, A History of Medicine. New York, O x f o r d University Press, vol. 1, 1951, p. 106. 2. Martin Levey, Chemistry and Chemical Technology in Ancient Mesopotamia. Amsterdam, Elsevier Publishing Co., 1959, pp. 147-156. 3. W. R. Dawson, "Egypt's Place in Medical History," in Science and Medicine in History: Essays in Honour of Charles Singer. London, O x f o r d University Press, 1953, vol. I, pp. 47-60. 4. J. B. de C. M. Saunders, The Transition from Ancient Egypt to Greek Medicine. Lawrence, University of Kansas Press, 1963, pp. 21-27.

2 Biochemical Concepts in Classic Greece 1. J . B. de C. M. Saunders, The Transition from Ancient Egypt to Greek Medicine. Lawrence, University of Kansas Press, 1963, pp. 8-11. 2. O. T e m k i n , "Greek Medicine as Science a n d Craft," Isis 44 (1953), 213-225. 3. L. Edelstein, " T h e Relation of Ancient Philosophy to Medicine," Bull. Hist. Med. 26 (1952), 299-316. 4. J o h n Burnet, Early Greek Philosophy. 3rd ed., London, A. and C. Black, 1920, pp. 70-71. 5. Ibid., p. 74. 6. Fragment 42 in Ibid., p. 136.

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Notes to Pages 8-18

7. Ibid., p. 151. 8. Ibid., pp. 151-153. 9. Τ. S. Hall, "The Scientific Origins of the Protoplasm Problem," J. Hist. Ideas 11 (1950), 339-356. 10. R. E. Siegel, "Hippocratic Description of Metabolic Diseases in Relation to Modern Concepts," Bull. Hist. Med. 34 (1960), 355-365. 11. Burnet, Greek Philosophy, p. 201; W. H. S. Jones, "Philosophy and Medicine in Ancient Greece," Bull. Hist. Med. supp. 8 (1946), 10-13. 12. Fragment 100 in Burnet, Greek Philosophy, p. 219. 13. Ibid., p. 230. 14. Ibid., pp. 242-245. 15. Ibid., pp. 245-246. 16. Fragment 100 in Ibid., p. 219. 17. Ibid., p. 201. 18. Ibid., p. 264. 19. Ibid., pp. 193-196; Jones, "Philosophy and Medicine," pp. 3-6. 20. A. D. Winspear, The Genesis of Plato's Thought, New York, Dryden Press, 1940, pp. 154-156; G. S. Kirk and J . E. Raven, The Presocratic Philosphers, Cambridge, Cambridge University Press, 1957, p. 234. 21. Hippocrates, trans. W. H. S.Jones, Loeb Classical Library, London, W. Heinemann, 1923-1931, vol. 1, pp. 23-25. 22. Ibid. 23. Jones, "Philosophy and Medicine." 24. Hippocrates, "On Ancient Medicine," vol. 1, p. xiv. 25. Ibid., " T h e Nature of Man," vol. 4, p. iv. 26. E. Schöner, "Das Vierschema in der antiken Humorpathologie," Sudhoff s Arch., 1964 Beihefte 4, pp. 20-21. 27. Η. W. Miller, "The Concept of Dynamis in De Victu," Trans. Am. Philological Assn. 90(1959) 147-164. 28. Hippocrates, "On Nutriment," vol. 1, p. xliv. 29. Ibid., p. xxxvi. 30. Ibid., "Regimen I," vol. 4, p.vii. 31. Ibid., p. ix. 32. Siegel, "Hippocratic Description." 33. Hippocrates, "On Nutriment," p. xxvii 34. Ibid., p. xxxv. 35. Siegel, "Hippocratic Description." 36. Hippocrates, "On Nutriment," vol 1, p. li. 37. Winspear, Plato's Thought, p. 118. 38. Plato, Timaeus, trans. Benjamin Jowett, New York. Library of Liberal Arts, 1949, p. 62. 39. Winspear, Plato's Thought, p. 159. 40. H. D. Hantz, " T h e Biological Motivation in Aristotle," unpubl. Ph.D. thesis, Columbia University, New York, 1939. 41. Ingemar Düring, Aristotle's Chemical Treatise, Meteorologica Book IV, Göteborg, Elanders boktryckeri aktiebolag, 1944, p. 10.

Notes to Pages 18-25

239

42. Whether this book was written by Aristotle himself or by one o f his pupils, it certainly reflects his ideas. 43. During, Meteorologica, pp. 35-40. 44. Schöner, "Vierschema" pp. 66-67. 45. Aristotle, " O n the Generation o f Animals," trans. Arthur Piatt, in The Works of Aristotle, Oxford, Clarendon Press, 1912, vol. 5, 730b, 1-25. 46. A. L. Peck, " T h e Connate Pneuma: An Essential Factor in Aristotle's Solutions to the Problems o f Reproduction and Sensation," in Science and Medicine in History: Essays in Honour of Charles Singer, London, Oxford University Press, 1953, pp. pp. 111-121. 47. F. M. Cornford, Before and After Socrates, Cambridge, Cambridge University Press, 1932, pp. 63-64. 48. Hantz, Biological Motivation, p. 17. 49. Aristotle, "On the Progress o f Animals," trans. A. S. L. Farquharson, in The Works of Aristotle, Oxford, T h e Clarendon Press, 1912, vol. 5, 704b, 15. 50. Hantz, Biological Motivation, p. 32. 51. Aristotle, " O n the Parts o f Animals," trans. William Ogle, in The Works of Aristotle, Oxford, Clarendon Press, 1912, vol. 5, II, 646a, 10-25. 52. Aristotle, " O n the Soul," trans. J . A. Smith, in The Basic Works of Aristotle, ed. Richard McKeon, New York, Random House, 1941. 53. Hantz, Biological Motivation, p. 32. 54. Peck, "Connate Pneuma." 55. Ibid. 56. Aristotle, "Generation o f Animals," I, 729a, 10-15. 57. Ibid., II, 736a, 1-20. 58. Ibid., 717a, 15-20; 716b, 1. 59. Ibid., II, 745b, 20-30. 60. Ibid., IV, 777a, 5. 61. Aristotle, " O n the Parts o f Animals," II, 650a. 62. Ibid., II, 650b, 15-35; 651a, 1-20. 63. Ibid., I I I , 668a, 30-35. 64. Ibid., II, 651a, 20-25; 651b, 1-20. 65. Aristotle, "Generation o f Animals," II, 744b, 10-35; 745a, 1-20. 66. E. Clark, "Aristotelian Concepts o f the Form and Function o f the Brain," Bull. Hist. Med. 37 (1963), 1-14. 67. Aristotle, "Parts o f Animals," II, 652a, 20-35. 68. Ibid., I I I , 669b-672b. 69. Ibid., IV, 677a, 5-30.

3 The Hellenistic Period 1. George Sarton, A History of Science. Hellenistic Science and Culture in the Last Three Centuries B.C. Cambridge, Mass., Harvard University Press, 1959, pp. 220-223.

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Notes to Pages 26-33

2. J. F. Dobson, "Erasistratos," Proe. Royal Soc. Med. (London) 20 (1927), 825-832. 3. L. G. Wilson, "Erasistratos, Galen, and the P n e u m a "Bull. Hist. Med. 33 (1959), 293-314. 4. Dobson, "Erasistratos." 5. W. H. S. Jones, The Medical Writings of Anonymus Londinensis, Cambridge, Cambridge University Press, 1947. 6. Ibid., pp. 1-8. 7. Ibid., pp. 53-55. 8. Ibid., pp. 33-34. 9. Ibid., p. 81 10. Ibid., p. 83. 11. Ibid., pp. 97-101. 12. Ibid., pp. 115-119. 13. Ibid., p. 119. 14. Ibid., pp. 85-87. 15. Ibid., p. 127. 16. Ibid., pp. 139-141. 17. S. Sambursky, Physics of the Stoics. London, Macmillan, 1959, pp. 22-25. 18. Ibid., p. 45. 19. E. Schöner, "Das Vierschema in der antiken Humorpathologie," Sudhoff s Arch. 1964, Beihefte 4, pp. 79-80. 20. Sambursky, Stoics, p. 35. 21. Lucretius, The Nature of the Universe, trans. R. E. Latham, Baltimore, Penguin Classics, 1951, book IV, 823-876. 22. Ibid., book IV, 628, 694. 23. R. G. H o m e , "Atomism in Ancient Medical History," Med. Hist. 7 (1963), 317-329. 24. George Sarton, Galen of Pergamon. Lawrence, University of Kansas Press, 1954, pp. 30-38. 25. Schöner, "Vierschema," p. 93. 26. F. Kremers and G. U r d a n g , History of Pharmacy, 3rd ed. rev. by G. Sonnedecker, Philadelphia, Lippincott, 1963, p. 16. 27. R. H. Shryock, "Quantification in Medical Science," Isis 52 (1961), 217. 28. W. H. S. Jones, "Ancient Documents and Contemporary Life with Special Reference to the Hippocratic Corpus, Celsus, and Pliny," in Science and Medicine in History; Essays in Honour of Charles Singer. London, O x f o r d University Press, 1953, pp. 100-110. 29. Sarton, Galen of Pergamon, p. 65. 30. Galen, "On the Uses of the Parts," in Oeuvres anatomiques, physiologiques et medicales de Galten, C. Daremberg, ed., Paris, Bailliere, 1854-1856, p. 313. 31. Ibid., p. 332.

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32. An English translation is by Margaret Tallmadge May, Galen on the Usefulness of the Parts of the Body, Ithaca, N.Y., Cornell University Press, 1968. 33. C. E. A. Winslow and R. R. Bellinger, "Hippocratic and Galenic Concepts of Metabolism,"/. Hist. Med. 17 (1945), 127-137. 34. Galen, On the Natural Faculties, trans. A. J. Brock, Loeb Classical Library, London, W. H e i n e m a n n , 1916, III, vii. 35. Daremberg, Galien, p. 279; "On Habits," Ibid., pp. 87, 102; also in A. J. Brock, Greek Medicine, London, J . M. Dent and Sons, 1929, p. 186.

36. O . T e m k i n , "On Galen's Pneumatology," Ge.mm/5 8 (1956), 180-189. 37. Galen, "On Habits," pp. 103-104. 38. Galen, Natural Faculties, II. 39. Wilson, "Erasistratos." 40. Galen, Natural Faculties, I, v. 41. Ibid., I, vi. 42. Ibid., III, i. 43. Ibid., III, iv. 44. Ibid., I, x. 45. Ibid., II, iii. 46. Lester S. King, The Growth of Medieval Thought. Chicago, University of Chicago Press, 1963, pp. 65-79.

4 The Early Middle Ages 1. M. Clagett, Greek Science in Antiquity, 2 n d ed. New York, Collier Books, 1963, pp. 148-149. 2. W. Stahl, Roman Science. Madison, University of Wisconsin Press, 1962, pp. 65-72. 3. Ibid., pp. 74-77. 4. Ibid., pp. 170-172. 5. Ibid., pp. 68, 142. 6. Clagett, Greek Science, p. 187. 7. Stahl, Roman Science, pp. 213-223. 8. W. D. Sharpe, "Isidore of Seville, the Medical Writings." Trans. Am. Phil. Soc. n. s. 54, part 2 (1964), p. 15. 9. Ibid., p. 47. 10. Ibid., p. 56. 1 1 . H . Sigerist, " T h e Latin Medical Literature of the Early Middle Ages." J. Hist. Med. 13 (1958), 127-146. 12. J. Stannard, "Benedictus Crispus, an Eighth Century Medical P o e t , " / . Hist. Med. 21 (1966), 24-46 13. E. Mendelsohn, Heat and Life. Cambridge, Mass., Harvard University Press, 1964, p. 22.

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Notes to Pages 41-48

14. For a discussion of the factors responsible for the origin a n d growth of alchemy, see Η . M. Leicester, Historical Background of Chemistry. New York, Wiley, 1956, p p . 32-47. 15. O. T e m k i n , "Medicine a n d Graeco-Arabic Alchemy," Bull Hist. Med. 29 (1955), 134-153. 16. Clagett, Greek Science, p. 221. 17. O . T e m k i n , "Studies o n Late A l e x a n d r i a n Medicine. I. A l e x a n d r i a n C o m m e n t a r i e s o n Galen's D e Seeds a n d I n t r o d u c e n d o s . " Bull. Hist. Med. 3 (1935), 405-430. 18. L. G. Westerink, "Philosophical Medicine in Late Antiquity "Janus 51 (1964), 169-177. 19. M. M e y e r h o f , " T h e E n d of t h e School of A l e x a n d r i a A c c o r d i n g to S o m e A r a b A u t h o r s , " Archeion 15 (1933), 1-15. 20. Μ. M e y e r h o f , " V o n A l e x a n d r i e n nach B a g h d a d , " Sitz. Preuss. Akad. Wiss., Phil.-Hist. Klasse (1930), 389-429.

5 Chinese and Indian Concepts 1. T h e most c o m p l e t e analysis of all phases of Chinese philosophy as it is related to Chinese science is J . N e e d h a m , Science and Civilization in China, vol. 2, History of Scientific Thought. Cambridge, Cambridge University Press, 1962. T h e section o n T a o i s m is o n p p . 33-164. 2. Ibid., p p . 35-36. 3. Ibid., p p . 216-278. 4. Ibid., p p . 274-287. 5. Ibid., p p . 296-297. 6. Ibid., p p . 239-244. 7. See t h e tables of these categories, Ibid., p p . 262-263. 8. Ibid., p. 47. 9. Ibid., p p . 55-56. 10. Ibid., p p . 153-154. 11. Ibid., p p . 139-152. 12. J . R. W a r e , Alchemy, Medicine, Religion in the China of A. D. 320. C a m bridge, Mass., M.I.T. Press, 1966. 13. Ibid., p p . 139-140. 14. Ibid., p. 290. 15. Ibid., p.5. 16. Ibid., p. 140. 17. For a discussion of C h i n e s e alchemy see Η . M. Leicester, Historical Background of Chemistry, New York, Wiley, 1956, pp. 53-61. 18. I. Veith, The Yellow Emperor's Classic of Internal Medicine. Baltimore, Williams a n d Wilkins, 1949. 19. Ibid., p p . 19-21 20. Ibid., p. 25.

Notes to Pages 4 8 - 5 5

243

21. Ν. Τ . Huan, "Esquisse d'une histoire de la biologie chinoise des origines jusqu'au IV e siecle," Rev. hist. sei. 10 (1957), 1-37. 22. Veith, Yellow Emperor, pp. 58-76. 23. Ibid., pp. 53-58. 24. Ε. H. Hume, The Chinese Way in Medicine. Baltimore, J o h n s Hopkins Press, 1940, p. 152. 25. T ' a o Lei, "Historical Notes on Some Vitamin Deficiency Diseases in China," Chinese Med. J. 58 (1940), 314-323. 26. G. D. Lu and J . Needham, "Medieval Preparation o f Urinary Steroid Hormones," Nature 200 (1963), 1047-1048; Med. Hist. 8 (1964), 101-121. 27. J . Filliozat, The Classical Doctrine of Indian Medicine. Delhi, Munshiram Manoharlal, 1964, p. 238. 28. P. Kutumbiah, "Post Vedic Medicine," Indian J. Hist. Med. 4 (1959), 1-9. 29. H. R. Zimmer, Hindu Medicine. Baltimore, J o h n s Hopkins Press, 1948, pp. 3-8. 30. Ibid., pp. 17-18. 31. Kutumbiah, "Post Vedic Medicine." 32. P. Ray and Η. N. Gupta, Caraka Samhita, a Scientific Synopsis. New Delhi, National Institute of Science of India, 1965, pp. 1-3. 33. Ibid., p. 5. 34. Zimmer, Hindu Medicine, pp. 134-150. 35. Ibid., p. 184. 36. Ray and Gupta, Caraka Samhita, pp. 18-19. 37. Zimmer, HiTidu Medicine, pp. 187-189. 38. Ray and Gupta, Caraka Samhita, pp. 7-10. 39. D. V. Subba Reddy, "Influence o f Indian Medicine on Arabian and Persian Medical Literature," Indian J. Hist. Med. 4, no. 2 (1959), 23-34.

6 Arabic Concepts 1. I. A. Brody, J r . , " T h e School o f Medicine at J u n d i Shapur, the Birthplace o f Arabic Medicine," Trans. Coll. Physicians Philadelphia 23 (1955), 29-37. 2. C. Elgood, A Medical History of Persia and the Eastern Caliphate. Cambridge, Cambridge University Press, 1951, p. 97. 3. Ibid., p. 102. 4. M. Meyerhof, "New Light on Hunain ibn Ishaq and His Period," Isis 8 (1926), 685-724. 5. Μ. Levey, "Some Facets o f Mediaeval Arabic Pharmacology," Trans. Coll. Physicians Philadelphia 3 0 (1963), 157-162. 6. Η. M. Leicester, Historical Background of Chemistry. New York, Wiley, 1956, p. 66.

244

Notes to Pages 5 5 - 6 0

7. Ο. Temkin, "Medicine and Graeco-Arabic Alchemy," Bull. Hist. Med. 29 (1955) 134-153. 8. S. Hamarneh, "Chemical Therapy in T e n t h Century Arabic Medicine," Am. J. Pharm. Educ. 26 (1962), 12-18. 9. Levey, "Arabic Pharmacology," 10. M. Levey, "Studies in Development o f Atomic Theory," Chymia 7 (1961) 40-49. 1 1 . M . Levey, The Medical Formulary or Aqrabadhin of al-Kindi. Madison, University of Wisconsin Press, 1966, pp. 33-34. 12. For the early history of this concept, see A. O. Lovejoy, The Great Chain of Being. Cambridge, Mass., Harvard University Press, 1936, pp. 24-66. 13. Leicester, Historical Background, pp. 63-67. 14. M. Levey, "Arab Mineralogy of the T e n t h Century," Chymia 12 (1967), 15-26. 15. S. H. Nasr, Three Muslim Sages. Cambridge, Mass., Harvard University Press, 1964, pp. 38-40. 16. M. Schipperges, "Die arabische Medizin als Praxis und als Theorie." Sudhoffs Arch. 4 3 (1959), 317-328; "Eine griechisch-arabische Einfuhrung in die Medizin," Deutsch. Med. Wochschr. 87 (1962), 1675-1680. 17. F. S. Bodenheimer, " T h e Biology o f Abraham ben David Halevy o f Toledo " Arch Int. Hist. Sei. n. s. 4 (1951), 39-62. 18. S. Hamarneh in his review of Μ. Η. Shah, The General Principles of Avicennas Canon of Medicine, f . Hist. Med. 23 (1968), 312-313. 19. O. C. Gruner, A Treatise on the Canon of Medicine of Avicenna, Incorporating a Translation of the First Book. London, Luzac, 1930. 20. H. C. Krueger, Avicenna's Poem on Medicine. Springfield, 111., Thomas, 1963. 21. Gruner, Treatise, pp. 25-33. 22. C. Elgood, "Tibb-ul-Nabbi or Medicine o f the Prophet," Osiris 14 (1962), 33-192. 23. Krueger, Poem, pp. 16-18. 24. Ibid., p. 19. 25. Ibid., pp. 19-20; Gruner, Treatise, p. p. 93. 26. Gruner, Treatise, p. 112. 27. E. G. Browne, Arabian Medicine. Cambridge, Cambridge University Press, 1921, pp. 121-125. 28. Gruner, Treatise, p. 99. 29. R. D. Clemens, "Avicenna the Prince o f Physicians. Part I I , " Minnesota Medicine 4 9 (1965), 187-192. 30. W. W. Thorns, " T h e Story of a Book," Univ. Michigan Med. Bull. 22 (1956), 227-237. 31. M. Levey, "Medieval Arabic Toxicology. T h e Book of Poisons of Ibn Washiya and Its Relationship to Early Indian and Greek Texts." Trans. Am. Philosoph. Soc. 56, part 7 (1966), p. 16.

Notes to Pages 60-67

245

32. Ibid., pp. 25-26. 33. Elgood, "Tibb-uI-Nabbi." 34. Arabian Nights, Trans. Richard Burton. Privately printed for the Burton Club, Vol. 5, pp. 196, 218-226. 35. M. Levey, "Some Eleventh Century Medical Questions Posed by Ibn Butlan and Later Answered by Ibn Ithirdi," Bull. Hist. Med. 39 (1965), 495-507. 36. M. Meyerhof, "Ibn an-Nafis (XIII Cent.) and His T h e o r y of the Lesser Circulation," Isis 23 (1935), 100-120; Ε. Ε. Bittar, "A Study of Ibn Nafis "Bull. Hist. Med. 29 (1955) 352-368. 37. Ε. E. Bittar, " T h e Influence of Ibn Nafis. A Linkage in Medical History," Univ. Michigan Med. Bull. 22 (1956) 274-278; E. D. Coppola, " T h e Discovery of the Pulmonary Circulation," Bull. Hist. Med. 31 (1957), 44-77. 38. Η. H. Lauer, " G r u n d z u g e einer medizinischen T h e o r i e in d e r Kulturmorphologie Ibn Chalduns," Centaurus 11 (1965) 111-127.

7 The Medieval Period 1. P. Ο. Kristeller, " T h e School of Salerno," Bull. Hist. Med. 17 (1945), 138-194. 2. L. T h o r n d i k e , A History of Magic and Experimental Science. New York, Macmillan, 1923, vol. I, pp. 742-759. 3. H. Schipperges, "Die Assimilation der arabischen Medizen durch d e n lateinische Mittelalter," Sudhoffs Arch. supp. 3 (1964), 29-34. 4. A translation of the Isogogue is given by H. P. Cholmely, John of Gaddesden and the Rosa Medicinae. O x f o r d , Clarendon Press, 1912. T h e quotation is on p. 145. 5. Schipperges, "Assimilation," pp. 102-103. 6. F. C. Coppleston, Medieval Philosophy. London, Methuen, 1952; H a r p e r Torchbooks, New York, H a r p e r Row, 1961, p. 55. 7. T h o r n d i k e , Magic, vol. 2, pp. 56-57. 8. Schipperges, "Assimilation," pp. 81-83. 9. V. L. Bullough, " T h e Development of the Medical University at Montpellier to the E n d of the Fourteenth Century," Bull. Hist. Med: 30 (1956), 508-523. 10. V.L. Bullough, " T h e Medieval Medical University at Paris," Bull. Hist. Med. 31 (1957), 197-211. 1 1 . H . E. Handerson, Gilbertus Anglicus. Cleveland, Ohio, Cleveland Medical Library Association, 1918, p. 28. 12. T h o r n d i k e , Magic, vol. 2, p. 507. 13. Ibid., pp. 886-887. 14. J . N e e d h a m , A History of Embryology, 2nd ed. New York, AbelardSchuman, 1959, p. 30.

246

Notes to Pages 67-78

15. C. Probst, "Der Weg des ärztlichen Erkennens bei Heinrich von Mondeville" in Fachliteratur des Mittelalters, ed. G. Keil, R. Rudolf, W. Schmitt, H. J . Vermeer. Stuttgart, J. B. Metzler, 1968, pp. 351-352. 16. Guy's ideas are extensively analyzed by M. S. O g d e n , "Guy d e Chauliac's T h e o r y of the H u m o r s , " J. Hist. Med. 24 (1969), 272-291. 17. W. Pagel, Paracelsus. An Introduction to Philosophical Medicine in the Era of the Renaissance. Basel, S. Karger, 1958, p. 173. 18. T h o r n d i k e , Magic, vol. 3, pp. 244-245. 19. Pagel, Paracelsus, pp. 174-177. 20. T h o r n d i k e , Magic, vol. 2, pp. 124-154. C. Singer, " T h e Scientific Views and Visions of Saint Hildegard (1098-1180)" in Studies in the History and Methods of Science, ed. Charles Singer. O x f o r d , Clarendon Press, 1917, vol. 1, pp. 1-55. 21. E. Strübing, " N a h r u n g u n d E r n ä h r u n g bei Hildegard von Bingen, Abtissen, Ärztin u n d Naturforscherin (1098-1179)," Centaurus 9 (1963), 73-124. 22. Ibid., p. 85. 23. T h o r n d i k e , Magic. Singer, "Saint Hildegard." 24. T h o r n d i k e , Magic, vol. 2, p. 154. 25. Strübing, "Hildegard," pp. 97-98. 26. Β. Η. Hill, Jr., " T h e Grain and the Spirit in Medieval Anatomy," Speculum 40 (1965), 63-73. 27. N e e d h a m , Embryology, pp. 86-87. 28. Ibid., p. 93. 29. Hill, " T h e Grain." 30. Coppleston, Medieval Philosophy, p. 87. 31. J. Candlish, "St. T h o m a s Aquinas a n d the Dynamic State of Body C o n s t i t u e n t s , " / Hist. Med. 23 (1968) 272-275. 32. V. R. Larkin, "St. T h o m a s Aquinas on the Movement of the Heart," J. Hist. Med. 15 (1960), 22-20. 33. T h o r n d i k e , Magic, vol. 2, p. 671. 34. J. Charles, "Roger Bacon on the Errors of Physicians," Med. Hist. 4 (1960), 269-282. 35. W. Pagel a n d M. Winder, "Gnostisches bei Paracelsus u n d K o n r a d von Megenberg," in Fachliteratur, pp. 359-371. 36. Ε. Strübing, "Konrad von Megenberg: 'Buch d e r Natur' die älteste deutschsprächige Quelle zur Geschichte der menschlichen E r n ä h r u n g , " Ernährungsforschung 9 (1964), 190-211. 37. R. P. Multhauf, The Origins of Chemistry. London, Oldbourne, 1966, pp. 151-152. 38. Pagel, Paracelsus, p. 252. 39. Multhauf, Origins, pp. 204-205. 40. R. P. Multhauf, "John of Rupescissa a n d the Origin of Medical Chemistry," Isis 45 (1954), 359-367. 41. Pagel, Paracelsus, p. 264. 42. Multhauf, "John of Rupescissa."

Notes to Pages 7 8 - 8 9

247

43. R. P. Multhauf, " T h e Significance of Distillation in Renaissance Medical Chemistry," Bull. Hist. Med. 30 (1956), 329-346. 44. Thorndike, Magic, vol. 4, pp. 73-75. 45. H. Viets, "De Staticis E x p e r i m e n t s of Nicolaus Cusanus,"^nn. Med. 'Hist. 4 (1922), 115-135. Pp. 126-135 contain a translation of the fourth book o f The Idiot. 46. Η. E. Hoff, "Nicolaus o f Cusa, Van Helmont, and Boyle. T h e First Experiment o f the Renaissance in Quantitative Biology and Medicine," J. Hist. Med. 19 (1964), 99-117.

8 Paracelsus and the Beginnings of Iatrochemistry 1. Η. M. Pachter, Paracelsus, Magic into Science. New York, Henry Schuman, 1951. W. Pagel, Paracelsus. An Introduction to Philosophical Medicine in the Era of the Renaissance. Basel, S. Karger, 1958, pp. 5-49. 2. Ibid., pp. 203-350. W. Pagel. "Paracelsus and the Neoplatonic and Gnostic Tradition," Ambix 8 (1960), 125-166. W. Pagel, " T h e Prime Matter o f Paracelsus," Ambix 9 (1961), 117-135. 3. O. Temkin, " T h e Elusiveness of Paracelsus," Bull. Hist. Med. 2 6 (1952), 201-217. 4. Pagel. Paracelsus, pp. 68-71. 5. Pachter, Paracelsus, p. 41. 6. W. Pagel and P. Rattansi, "Vesalius and Paracelsus," Med. Hist. 8 (1964), 309-328. 7. Pagel, Paracelsus, p. 59. 8. Ibid., pp. 89-96. 9. Ibid., pp. 100-104. 10. Ibid., pp. 104-106. 11. Ibid., p. 178. 12. Ibid., pp. 153-161. 13. Pachter, Paracelsus, p. 56. 14. Pagel, Paracelsus, pp. 141-149. 15. T . P. Sherlock, " T h e Chemical Work o f Paracelsus," Ambix 3 (1948), 33-63. 16. Pagel, Paracelsus, pp. 190-192. 17. Ibid., pp. 158-161. 18. W. Pagel, " T h e Wild Spirit (Gas) of J o h n Baptist Van Helmont (1579-1644) and Paracelsus," Ambix 10 (1962), 1-13. 19. A. G. Debus, " T h e Paracelsian Aerial Niter," Isis 55 (1964), 43-61. 20. Pachter, Paracelsus, p. 223. 21. Pagel, Paracelsus, p. 158. 22. Ibid., p. 294. 23. Κ. E. Rothschuh, "Der Begriff der 'Physiologie' und sein Bedeutungswandel in der Geschichte der Wissenschaft," Arch. int. Hist. Sei. 10 (1957), 209-210. 24. Pagel, Paracelsus, p. 311.

248

Notes to Pages 89-98

25. R. P. Multhauf, The Origins of Chemistry, London, Oldbourne, 1966, p. 291. 26. Ibid., pp. 290-293. 27. A. G. Debus, The English Paracelsians. New York, Franklin Watts, 1966, pp. 36-37. 28. Pagel, Paracelsus, pp. 311-333. 29. Debus, English Paracelsians, pp. 91-95. 30. Ibid., pp. 49-85. 31. L. T h o r n d i k e , History of Magic and Experimental Science. New York, Macmillan, 1958, vol. 7, pp. 153-202. 32. R. Multhauf, "Medical Chemistry and 'the Paracelsians,' "Bull. Hist. Med. 28 (1954), 101-126. 33. R. Shryock, "Quantification in Medical Science," Isis 52 (1961), 220222. 34. A. G. Debus, The Chemical Dream of the Renaissance. Cambridge, England, H e f f e r , 1968.

9 The Transitional Seventeenth Century 1.J. R. Partington, A History of Chemistry. London, Macmillan, 1961. vol. 2, pp. 223-255. 2. Marie Boas, "An Early Version of Boyle's Sceptical Chymist," Isis 45 (1954), 153-168. 3. Ibid., pp. 166-168. 4. C. Webster, "Water as the Ultimate Principle of Nature. T h e Backg r o u n d to Boyle's Sceptical Chymist," Ambix 13 (1966), 96-107. 5. E. H o f f , "Nicolaus of Cusa, Van Helmont, a n d Boyle. T h e First Experiment of the Renaissance in Quantitative Biology and Medicine," J. Hist. Med. 19 (1964), 99-117. 6. Partington, History, pp. 229-231. 7. W. Pagel, " T h e 'Wild Spirit' (Gas) of J o h n Baptist Van Helmont (1579-1644) and Paracelsus," Ambix 10 (1962), 1-13. 8. W. Pagel, " T h e Religious and Philosophical Aspects of Van Helmont's Science a n d Medicine," Bull. Hist. Med. supp. 2 (1944), p. 18. 9. Partington, History, pp. 656-657. 10. Pagel, "Religious a n d Philosophical Aspects," pp. 6-7. 11. W. Pagel, "Van Helmont's Ideas on Gastric Digestion," Bull. Hist. Med. 30 (1956), 529. 12. Ibid., pp. 530-533. 13. Pagel, "Religious a n d Philosophical Aspects," pp. 14-15. 14. R. P. Multhauf, "J. B. Van Helmont's Reformation of the Galenic Doctrine of Digestion," Bull. Hist. Med. 29 (1955), 154-163. 15. Pagel, "Religious a n d Philosophical Aspects," p. 39. 16. Ibid., p. 40. 17. Ibid., p. 40-41.

Notes to Pages 98-107

249

18. Partington, History, p. 239. 19. W. Pagel, William Harvey's Biological Ideas. Basel, H a f n e r , 1967, pp. 252-257, 343. 20. L. T h o r n d i k e , A History of Magic and Experimental Science. New York, Macmillan, 1958, vol. 7, p. 517. 21. Ibid., vol. 8, pp. 436-440. 22. H o m e r W. Smith, " T h e Biology of Consciousness," in The Historical Development of Physiological Thought, ed. C. M. Brooks a n d P. F. Cranefield. New York, H a f n e r , 1959, pp. 111-115. 23. Michael Foster, Lectures on the History of Physiology During the Sixteenth, Seventeenth, and Eighteenth Centuries. Cambridge, Cambridge University Press, 1901, pp. 261-265; T . S. Hall, "Descartes' Physiological Method. Position, Principles, E x a m p l e s , " / . Hist. Biol. 3 (1970), 53-79; J . Jaynes, " T h e Problem of Animate Motion in the Seventeenth Century," J. Hist. Ideas 31. (1970), 219-234. 24. Foster, Lectures, p. 105. 25. Ibid., p. 109. 26. Partington, History, pp. 281-282. 27. Ibid., pp. 341-361. 28. Foster, Lectures, pp. 149-150. 29. Partington, History, p. 286. 30. Foster, Lectures, pp. 155-157. 31. Ibid., p. 158. 32. Ibid., p. 160. 33. Partington, History, p. 284. 34. Foster, Lectures, pp. 162-164. 35. T h o r n d i k e , Magic, Vol. 7, pp. 446-447. 36. D. McDonald, "Dr. J o h n Woodall a n d His T r e a t m e n t of Scurvy," Trans. Roy. Soc. Tropical Med. Hyg. 48 (1954) 360-365. 37. Partington, History, pp. 304-311. 38. Foster, Lectures, p. 275. 39. T h o r n d i k e , Magic, vol. 7, p. 520. 40. Ibid., Vol. 8, p. 525. 41. Ibid., p. 524. 42. Ibid., p. 148. 43. Foster, Lectures, pp. 82-83. 44. J. F. Fulton, Muscular Contraction and Reflex Control. Baltimore, Williams a n d Wilkins, 1926, p. 23. 45. Foster, Lectures, pp. 74-75. 46. R. Hierons a n d A. Meyer, "Willis's Place in the History of Muscle Physiology," Proc. Roy. Soc. Med. 57 (1964), 687-692. 47. Fulton, Muscular Contraction, p. 20. 48. Karl E. Rothschuh, Physiologie. Der Wandel ihre Konzepte, Probleme und Methoden von 16 bis 19 Jahrhundert. Munich, Karl Alber Freiberg Verlag, 1968, p. 111.

250

Notes to Pages 107-113

49. Mark Graubard, Circulation and Respiration. The Evolution of an Idea. New York, Harcourt, Brace and World, 1964, pp. 259-265. 50. Foster, Lectures, pp. 165-166. 51. Ibid., p. 82. 52. Marie Boas, Robert Boyle and Seventeenth Century Chemistry. Cambridge, Cambridge University Press. 1958, pp. 186-187. 53. Foster, Lectures, p. 179. 54. Phil. Trans. 2 (1667), 539; Graubard, Circulation, pp. 207-211. 55. Margaret 'Espinasse, Robert Hoohe. Berkeley, University of California Press, 1962, p. 52. 56. Charles A. Browne, "A Source Book in Agricultural Chemistry," Chronica Botanica 8, no. 1 (1944), 47. 57. Foster, Lectures, p. 181. 58. Graubard, Circulation, pp. 220-222. 59. J. R. Partington, "The Life and Work of John Mayow (1641-1679)," Isis 47 (1956), 217-230, 405-417. 60. Η. Guerlac, "John Mayow and the Aerial Niter." Actes du Septieme Congres International d'Histoire des Sciences, Jerusalem, 1953 pp. 332-349; Isis 45 (1954), 243-255. 61. Alan Debus, "The Paracelsian Aerial Niter," Isis 55 (1964), 43-61. 62. Partington, History, p. 591. 63. Ibid., pp. 611-612. 64. Ibid., pp. 593-597.

10 Physiology Comes of Age 1.E. A. Underwood, "Johann Gottfried Berger (1659-1736) of Wittenberg and His Textbook of Physiology (1701)," in Science and Medicine in History, ed. E. Ashworth Underwood. Oxford, Oxford University Press, 1953, vol. II, pp. 156-157. 2. J. R. Partington, A History of Chemistry. London, Macmillan, 1961, vol. 2, p. 657. 3. T h e psychology of Stahl is discussed by R. Koch, "Stahl," in Das Buch der grossen Chemiker, ed. G. Bugge. Berlin, Verlag Chemie, 1929, vol. 1, pp. 192-203. 4. L. S. King, "Stahl and Hoffmann. Α Study in Eighteenth Century Animism,"y. Hist. Med. 19. (1934), 118-130. 5. M. Foster, Lectures on the History of Physiology During the Sixteenth, Seventeenth, and Eighteenth Centuries. Cambridge, Cambridge University Press, 1901, p. 169. 6. Ibid., p. 171. 7. King, "Stahl and Hoffmann," pp. 121-124. 8. Foster, Lectures, pp. 224-226. 9. T. Hall, Ideas of Life and Matter. Chicago, University of Chicago Press, 1969, vol. 1, pp. 361-362.

Notes to Pages 113-120

251

10. C. Α. Browne, "A S o u r c e Book in Agricultural Chemistry," Chronica Botanica 8, no. 1 (1944), 103. 11. Foster, Lectures, p p . 171-172. 12. Partington, History, p. 674. 13. Foster, Lectures, p p . 226-227. 14. Partington, History, pp. 691-700. 15. King, "Stahl a n d H o f f m a n n . " 16. L. S. King, The Growth of Medical Thought. Chicago, University of Chicago Press, 1963, p. 163. 17. T h e d e v e l o p m e n t of fiber theory is discussed in detail by E. Bastholm, " T h e History of Muscle Physiology," Acta Historica Scientiarum naturalium et medicalium ( C o p e n h a g e n ) . 7 (1950), especially p p . 128-239. 18. King, Medical Thought, p p . 164-165. 19. Bastholm, "Muscle Physiology," pp. 233-235. 20. King, Medical Thought, p p . 166-168. 21. Ibid., pp. 169-170. 22. Ibid., pp. 172-173. 23. G. A. L i n d e b o o m , Herman Boerhaave. The Man and His Works. Lond o n , M e t h u e n , 1968. p p . 355-374. 24. F. R. J e v o n s , "Boerhaave's Biochemistry," Med. Hist. 6 (1962), 343362. 25. J . R. Baker, " T h e Cell T h e o r y . A Restatement, History, a n d Critique. Part 1," Quart. J. Microscop. Sei. 89 (1948), 110-112. 26. Hall, Ideas, p p . 373-374; L i n d e b o o m , Boerhaave, p p . 276-278. 27. Hall, Ideas, pp. 379-380. 28. F. W. Gibbs, " B o e r h a a v e a n d the Place of C h e m i s t r y in Medicine," in Chemistry in the Science of Medicine, ed. F. N. L. Poynter. L o n d o n , Pitm a n Medical Pub. Co., 1963, p p . 27-42. 29. Hall, Ideas, p. 377. 30. J e v o n s , "Boerhaave's Biochemistry," pp. 349-351. 31. Ibid., p. 353; F. R. J e v o n s , "Boerhaave's T e a c h i n g in Relation to Beccari's Identification of G l u t e n as an 'Animal' Substance," J. Hist. Med. 18 (1963), 174-175. 32. Partington, History, vol. 3, p. 546. 33. B r o w n e , "Source Book," p. 32. 34. E. F. Beach, "Beccari of Bologna. T h e Discoverer of Vegetable Prot e i n , " / . Hist. Med. 16 (1961), 354-373. 35. D. C. G o o d m a n , " T h e Application of Chemical Criteria to Biological Classification in t h e E i g h t e e n t h C e n t u r y , " Med. Hist. 15 (1971), 23-44. 36. J e v o n s , "Boerhaave's Biochemistry," p. 354. 37. Foster, Lectures, p. 204. 38. Hall, Ideas, p p . 375-376. 39. J e v o n s , "Boerhaave's Biochemistry," p p . 356-357. 40. L i n d e b o o m , Boerhaave, pp. 332-334; F. K u r z e r a n d P. M. S a n d e r son, " U r e a in the History of O r g a n i c Chemistry," f . Chem. Educ. 33 (1956), 452-459.

252

Notes to Pages 121-132

41. Lindeboom, Boerhaave, pp. 344-347. 42. Partington, History, vol. 2, pp. 751-752. 43. J. Parascandola and A. J . Ihde, "History of the Pneumatic T r o u g h , " Isis 60 (1969), 351-361. 44. Α. Haller, First Lines of Physiology, by the Celebrated Baron Albertus Haller. Presented under the Supervision of William Cullen. 2 vols., Edinburgh, 1786. 45. O. T e m k i n , A Dissertation on the Sensible and Irritable Parts of Animals by Albrecht von Haller. Baltimore, J o h n s Hopkins Press, 1936. p. 8. 46 Hall, Ideas, pp. 393-394. 47. Haller, First Lines, vol. 1, p. 80. 48. Ibid., p. 161. 49. Ibid., p. 153. 50. Ibid., pp. 217-221. 51. Foster, Lectures, pp. 297-298. 52. F. W. Home, "Electricity and the Nervous Fluid," J. Hist. Biol. 3 (1970), 235-251. 53. Haller, First Lines, p. 223. 54. Bastholm, "Muscle Physiology," pp. 219-225. 55. T e m k i n , Dissertation. 56. Haller, First Lines, vol. 2, p. 79. 57. Ibid., pp. 86-87. 58. Ibid., p. 103. 59. Ibid., pp. 122-125. 60. Ibid., pp. 146-147. 61. Ibid., p. 157. 62. Hall, Ideas, vol. 2, p. 89. 63. de R e a u m u r , "Sur la digestion des oiseaux." Mem. Acad. Roy. Sei. (1752), 266-307. 64. Foster, Lectures, pp. 212-219. 65. Partington, History, vol. 3, pp. 62-63. 66. Hall, Ideas, vol. 2, pp. 75-76.

11 Pneumatic Chemistry and its Biological Significance 1. A translation of this dissertation m a d e by C r u m Brown has been published by Leonard Dobbin, "Joseph Black's Inaugural Dissertation," / . Chem. Educ. 12 (1935), 225-228, 268-273. 2. Reprinted as Alembic Club Reprints, no. 1, "Experiments u p o n Magnesia Alba, Quick-lime, and Some O t h e r Alcaline Substances. By J o s e p h Black M. D. 1755." Edinburgh, 1898. 3. Dobbin, "Black's Dissertation," p. 227. 4. J . A. Cranston, "Black's Influence on Chemistry" in An Eighteenth Century Lectureship in Chemistry, ed. Andrew Kent. Glasgow, Jackson, 1950, pp. 99-106.

Notes to Pages 133-138

253

5. Q u o t e d by J o h n Read in "Joseph Black, the T e a c h e r and the Man" in Kent, Eighteenth Century Lectureship, p. 81. 6. J . R. Partington, A History of Chemistry. London, MacMillan, 1962, vol. 3, p. 247. 7. Ibid., p. 253. 8. Ibid., p. 259. 9. Ibid., pp. 285-286. 10. A. L. Lavoisier, "Experiences sur la respiration des animaux et sur les changements qui arrivent a l'air en passant par leur p o u m o n , " Mem. Acad. ray. Sei. 1777 (published 1780), 185-194. 11. G. Lusk, Nutrition. New York, Hoeber, 1933, p. 46. 12. Β. T . Scheer, " T h e Development of the Concept of Tissue Respiration," Ann. Sei. 4 (1939), 295-305. 13. A. L. Lavoisier, "Memoire sur la combustion en gene'ral," Mem. Acad. roy. Sei. 1777 (1780), 599-600. 14. Ε. A. Underwood, "Lavoisier a n d the History of Respiration," Proc. Roy. Soc. Med. 37 (1944), 247-262. 15. Partington, History, p. 428. 16. Ibid., p. 431. 17. Underwood, "Lavoisier," pp. 258-259. 18. Lusk, Nutrition, p. 61. 19. Ibid., pp. 61-62. 20. Partington, History, p. 474. 21. E. L. Scott, " T h e Macbride Doctrine of Air: an Eighteenth Century Explanation of Some Biochemical Processes, Including Photosynthesis," Ambix 17 (1970), 43-57. 22. J. Ingen-Housz, Experiments upon Vegetables, Discovering Their Great Power of Purifying the Common Air in Sunshine and Injuring It in the Shade and at Night. London, Elmsly and Payne, 1779. 23. Ε. I. Rabinowitch, Photosynthesis and Related Processes. New York, Interscience, 1945, vol. 1, pp. 12-19. 24. Ibid., pp. 19-22. 25. A. L. Lavoisier, "Reflexions sur la decomposition de l'eau par les substances vegetales et animales." Mem. Acad. roy. Sei. 1786 (1788), 590605. 26. Ν. Τ . de Saussure, Recherch.es chimiques sur la vegetation. Paris, Nyon, 1804. 27. Rabinowitch, Photosynthesis, pp. 23-24. 28. Partington, History, p. 284.

12 Animal Chemistry 1. R. Hooykaas, " T h e Experimental Origin of Chemical Atomic a n d Molecular Theories b e f o r e Boyle," Chymia 2 (1949), 77-78. 2. H. Guerlac, "Quantification in Chemistry," Isis 52 (1961), 201202.

254

Notes to Pages 139-144

3. D McKie, Antoine Lavoisier, Scientist, Economist, Social Reformer. New York, Schuman, 1952, pp. 274-288. 4. The difficulties resulting from this method are discussed by F. L. Holmes, "Elementary Analysis and the Origins of Physiological Chemistry," Isis 54 (1963), 52-53. 5. F. L. Holmes, "Analysis by Fire and Solvent Extractions: the Metamorphosis of a Tradition," Isis 62 (1971), 129-148. 6. L. J . Rather, "Some Relations between Eighteenth Century Fiber Theory and Nineteenth Century Cell Theory," Clio Medica 4 (1969), 191202. 7. W. R. Smeaton, Fourcroy, Chemist and Revolutionary 1755-1809. Cambridge, Heffer, 1962, pp. 163-166. 8. Ibid., p. 148. 9. Guerlac, "Quantification," p. 197. 10. J . R. Partington, Λ History of Chemistry. London, Macmillan, 1962, vol. 3, pp. 231-234. 11. Ibid., p. 215. 12. C. Hatchett, "Experiments and Observations on Shell and Bone," Phil. Trans. 89 (1799), 315-334. 13. W. H. Pepys in J . Fox, The Natural History of the Human Teeth. London, Thomas Cox, 1803, pp. 92-100. 14. T h e early literature on this controversy is reviewed in detail by Gerald Cox in Survey of the Literature of Dental Caries. National Academy of Sciences Publication 225, Washington, D.C., National Research Council, 1952, pp. 328-339. 15. Smeaton, Fourcroy, p. 146. 16. Partington, History, p. 78. 17. Holmes, "Elementary Analysis," pp. 55-56. 18. Partington, History, p. 502. 19. Ibid, pp. 446-447. 20. M. Teich, "On the Historical Foundation of Modern Biochemistry," Clio Medica 1 (1965), 41-57. 21. Holmes, "Elementary Analysis," pp. 55-59. 22. Smeaton, Fourcroy, pp. 139-140. 23. Holmes, "Elementary Analysis," p. 59. 24. Ibid., p. 61. 25. J . N. Halle, "Sur l'animalisation et l'assimilation des alimans," Ann. chim. 11 (1791), 158-174. 26. Holmes, "Elementary Analysis," p. 62. 27. J . J . Berzelius, A View of the Progress and Present State of Animal Chemistry, trans. Gustavus Brunnmark. London, J . Skirven, 1813. 28. Ibid., p. 3. 29. Ibid., p. 4. 30. Ibid., pp. 5-7. 31. Ibid., pp. 18-20.

Notes to Pages 144-151

255

32. Ibid., pp. 56-57. 33. Ibid., pp. 63-64. 34. Ibid., p. 75. 35. Ibid., p. 16. 36. J. Needham, The Chemistry of Life. Lectures on the History of Biochemistry. Cambridge, Cambridge University Press, 1970, p. xxvii. 37. Berzelius, View, pp. 114-115. 38. Teich, "Historical Foundation," p. 47. 39. Berzelius, View, pp. 77-80. 40. A. F. Fourcroy and N. L. Vauquelin, "Sur l'urine humaine," Ann. Ckim. 32 (1800), 152-153. 41. G. Lusk, Nutrition. New York, Hoeber, 1933, p. 66. 42. F. Magendie, "Sur les proprietes nutritives des substances qui ne contiennent pas d'azote," Ann. chim. phys. [2] 3 (1816), 66-77. 43. Holmes, "Elementary Analysis," p. 66. 44. J. L. Gay-Lussac and L.J. Thenard, "Extrait d'une memoire sur l'analyse vegetale et animale," Ann. chim. 74 (1810), 57-58. 45. Μ. E. Chevreul, Recherches chimiques sur les corps gras d'origine animale. Paris, F. G. Levrault, 1823. 46. W. Prout, "On the Ultimate Composition of Simple Alimentary Substances, with Some Preliminary Remarks on the Analysis of Organized Bodies in General," Phil. -Trans. 117 (1827), 355-388. 47. Η. B. Vickery, "The Origin of the Word Protein," Yale J. Biol. Med. 22 (1950), 387-393. 48. C. Schmidt, "Ueber Pflanzenchleim und Bassoin," Liebigs Ann. 51 (1844), 30.

13 Nineteenth-Century Vitalism 1. B. S. Jorgensen, "More on Berzelius and the Vital Force."/. Chem. Educ., 42 (1965), 394-396. 2. T. O. Lipman, "Reply to Jorgensen,"/. Chem. Educ. 42 (1965), 396397. 3. E. Mendelsohn, "Physical Modes and Physiological Concepts. Explanation in Nineteenth Century Biology," Brit. J. Hist. Sei. 2 (1965), 203219; see also R. Gullemin, "The Cahier Rouge of Claude Bernard," in Claude Bernard and Experimental Medicine ed. F. Grande and Μ. B. Visscher. Cambridge, Mass., Schenkman, 1967, pp. iv-v. 4. H. S. Klickstein, "Charles Caldwell and the Controversy in America over Liebig's 'Animal Chemistry,' " Chymia 4 (1953), 129-157. 5. M. Teich, "On the Historical Foundations of Modern Biochemistry," Clio Medica 1 (1965), 41-57. 6. O. Temkin, "Materialism in French and German Physiology in the Early Nineteenth Century," Bull. Hist. Med. 20 (1946), 323-327.

256

Notes to Pages 151-157

7. Τ . S. Hall, Ideas of Life and Matter, Chicago, University of Chicago Press, 1969, vol. 2, pp. 121-132. 8. Mendelsohn, "Physical Modes," 9. Ibid. See also Hall, Ideas, pp. 258-263. 10. T . O. Lipman, "Wöhler's Preparation of Urea a n d the Fate of Vitali s m , " / . Chem. Educ. 41 (1964), 452-458. R. C. Stauffer, "Speculation a n d Experiment in the Background of Oersted's Discovery of Electromagnetism,"/.sw 48 (1957), 34-36. 11. T e m k i n , "Materialism." 12. Hall, Ideas, pp. 171-178. 13. Ibid., pp. 210-211. 14. G. L. Geison, " T h e Protoplasmic T h e o r y of Life and the VitalistMechanist Debate," Isis 60 (1969), 273-292. 15. Ibid., p. 283. 16. Ibid., pp. 291-292. 17. Β. S. Jorgensen, "Berzelius u n d die Lebenskraft," Centaurus 10 (1965), 258-281. 18. J o r g e n s e n , "More on Berzelius," p. 394. 19. J o r g e n s e n , "Berzelius u n d die Lebenskraft," p. 272. 20. F. Wöhler, "Ueber die künstliche Bildung des Harnstoffe," PoggendorfsAnn. Phys. Chem. 12 (1828), 253-256. 21. T h e s e views are reviewed in detail by Lipman, "Wöhler's Preparation," and by J. Schiller, "Wöhler, l'ure'e et le vitalisme," Sudhoff 's Arch. 51 (1967), 229-243. 22. J.-L. Prevost a n d J.-A. Dumas, "Examen d u sang et de son action dans les divers p h e n o m e n e s d e la vie," Ann. chim. phys. 23 (1823), 90-104. 23. D. McKie, "Wöhler's 'Synthetic' Urea and the Rejection of Vitalism," Atowre 153 (1944), 608-610. 24. Ibid.; Schiller, "Wöhler." 25. J. J . Berzelius, fahresbericht über die Fortschritte der Chemie 11 (1832), 44-48. 26. J. H. Brooke, "Wöhler's Urea, and Its Vital Force?—A verdict f r o m the Chemists," Ambix 15 (1968), 84-114. 27. J. J . Berzelius, "Quelques idees sur u n e nouvelle force agissant dans les combinaisons des corps organiques," Ann. chim. phys. 61 (1836), 141161. 28. Brooke, "Wöhler's Urea". 29. H. Kolbe, "Beiträge zur Kentniss der gepaarten Verbindungen," LiebigsAnn. 54 (1845), 145-188. 30. M. Berthelot, Chimie organique fondee sur la synthese. Paris, MolletBachelier, 1860. 31. Schiller, "Wöhler." 32. Hall, Ideas, pp. 223-228. 33. W. Prout, Chemistry, Meteorology, and the Function of Digestion Considered with Reference to Natural Theology. 2nd ed., London, W. Pickering, 1834, p. 517.

Notes to Pages 157-163

257

34. Ibid., p. 419. 35. Ibid., p. 4 3 2 . 36. Ibid., p p . 434-437. 37. Ibid., p. 440. 38. Ibid., 419. 39. Ibid., p p . 428-429. 40. Τ . Ο . L i p m a n , "Vitalism a n d R e d u c t i o n i s m in Liebig's Physiological T h o u g h t , " Isis 58 (1967), 167-185. 41. Ibid., p p . 172-173. 42. Ibid., p. 185; Hall, Ideas, p p . 266-272. 43. Klickstein, " C h a r l e s Caldwell," p. 156. 44. P. F. C r a n e f i e l d , " T h e O r g a n i c Physics of 1847 a n d t h e Biophysics of T o d a y , " / Hist. Med. 12 (1957), 407-423. 45. T e m k i n , "Materialism," p. 327.

14

Theories of Digestion and Assimilation in Mid-Nineteenth Century

1. F. M a g e n d i e , Precis elementaire de physiologie. Paris, M e q u i g n o n Marvis, 1817, vol. 2, p. 13. 2. W. H . Brock, "William P r o u t o n T a s t e , Smell, a n d Flavor," J. Hist. Med. 22. (1967), 184-187. 3. W. P r o u t , " O n t h e N a t u r e of t h e Saline Matters Usually Existing in t h e S t o m a c h s of Animals," Phil. Trans. 114 (1824), 44-49. 4. A. M. Kasich, "William P r o u t a n d t h e Discovery of H y d r o c h l o r i c Acid in t h e Gastric J u i c e , " Bull. Hist. Med. 20 (1946), 340-358. 5 W. P r o u t , Chemistry, Meteorology, and the Function of Digestion Considered with Reference to Natural Theology. 2 n d ed., L o n d o n , W. Pickering, 1834, p p . 500-501. 6. F. T i e d e m a n n a n d L. G m e l i n , Die Verdauung nach Versuchen. Heidelb e r g a n d Leipzig, 1826-1827. 2 vols. F r e n c h t r a n s l a t i o n by A. J . L. J o u r d a n , Recherches experimentales, physiologiques et chimiques sur la digestion. Paris, Baillierre, 1827. vol. 1, p p . 335-336. All f u r t h e r r e f e r e n c e s a r e to the French translation. 7. Ibid., p. 363. 8. Ibid., p. 366. 9. Ibid., p p . 374-375. 10. W. B e a u m o n t , Experiments and Observations on the Gastric fuice and the Physiology of Digestion. P l a t t s b u r g h , Ν. Y., F. D. Allen, 1833. 1 1 . J . J . Bylebyl, "William B e a u m o n t , Robley D u n g l i s o n a n d t h e ' P h i l a d e l p h i a Physiologists,' " f . Hist. Med. 25 (1970), 3-21. 12. G. Rosen, The Reception of William Beaumont's Discovery in Europe. New York, S c h u m a n , 1942. p. 48. 13. Yieaumont, Experiments, p p . 78-79. 14. Ibid., p. 83. 15. Ibid., p. 84.

258

Notes to Pages 163-168

16. Ibid., pp. 34-35. 17. Tiedemann and Gmelin, Recherches, pp. 338-339. 18. Rosen, Reception, pp. 49-51. 19. Tiedemann and Gmelin, Recherches, p. 338. 20. J . Bostock, "Digestion," in The Encyclopedia of Anatomy and Physiology, ed. Robert Β. Todd. London, Longmans, 1839, vol. 2, p. 17. 21. C. Bernard and C. Barreswil, "Sur les phenomenes chimiques de la digestion," Compt. rend. 19 (1844), 1284-1289. 22. C. G. Lehmann, "Ueber die Saure Reaktion des Magensaftes," J. prakt. Chem. 40 (1847) 137-141. 23. F. Bidder and C. Schmidt, Die Verdauungssäfte und der Stoffwechsel. Mitau and Leipzig, G. A. Reyher, 1852, p. 44. 24. Ο. H. Wangensteen, "Claude Bernard's Work on Digestion," in Claude Bernard and Experimental Medicine, ed. F. Grande and Μ. B. Visscher. Cambridge, Mass., Schenkman, 1967, p. 46. 25. C. Bernard, Leqons de physiologie experimentale appliquees a la medecine. Paris, Baillie're, 1856, pp. 393-399. 26. Τ . Schwann, "Ueber das Wesen des Verdauungsprocesses," Liebigs Ann. 20 (1836), 28-34. 27. M. Teich, "On the Historical Foundation of Modern Biochemistry," Clio Medica 1 (1965), 41-57. 28. A. Payen and J . F. Persoz, "Memoire sur la diastase, les principaux produits de ses re'actions; et leurs applications aux arts industriels," Ann. chim. phys. 53 (1833), 73-92. 29. E. F. Leuchs, "Ueber die Verzucherung des Stärkmehls durch Speichel," Arch, gesamt. Naturlehre 3 (1831), 105-107. 30. L. Mialhe, "De la digestion et de l'assimilation des matieres sucrees et amiloi'des," Compt. rend. 20 (1845), 954-959. 31. Bouchardat and Sandras, "Des fonctions du pancreas et de son influence dans la digestion des feculantes," Compt. rend. 20 (1845), 10851091. 32. G. G. Valentin, Lehrbuch der Physiologie des Menschen. Braunschweig, F. Vieweg und Sohn, 1847, vol. 1, pp. 356-357. 33. C. Bernard, "Du sue pancreatique et de son röle dans les phenomenes de la digestion," Mem. soc. biol. 1 (1849), 99-115. 34. C. Bernard, Memoire sur le pancreas. Paris, Bailliere, 1856. 35. J . M. D. Olmsted and Ε. H. Olmsted, Claude Bernard and the Experimental Method in Medicine. New York, Schuman, 1952, p. 59. 36. C. A. Browne, "A Source Book of Agricultural Chemistry," Chronica Botanica 8. no. 1 (1944) 240. 37. J . Larner, "The Discovery of Glycogen and Glycogen Today" in Claude Bernard and Experimental Medicine ed. F. Grande and Μ. B. Visscher. Cambridge, Mass., Schenkman, 1967, p. 135. 38. Olmsted and Olmsted, Claude Bernard, p. 63. 39. Larner, "Glycogen," p. 136.

Notes to Pages 168-174

259

40. Μ. D. Grmek, "Barreswil." Dictionary of Scientific Biography, vol. 1, p. 471. 41. C. B e r n a r d , Du sue gastrique el de son role dans la nutrition. Paris, Rignoux, 1843. 42. C. Bernard, "Sur la mecanisme de la formation du sucre dans le foie." Compt. rend. 41 (1855), 461-469; M. D. Grmek, "First Steps in Claude Bernard's Discovery of the Glycogenic Function of the Liver," J. Hist. Biol. 1 (1968), 141-154. 43. C. B e r n a r d , "Sur la mecanisme physiologique d e la formation du sucre dans le foie." Compt. rend. 44 (1857), 578-586. 44. V. Hensen, "Ueber Zuckerbildung in d e r Leber," Virchow's Arch, path. Anat. Physiol., klin Med. 11 (1857), 395-398. 45. T h e edition of Liebig's Animal Chemistry or Organic Chemistry in Its Applications to Physiology and Pathology cited here is included in the volume Liebig's Complete Works on Chemistry, Philadelphia, Τ. B. Peterson. T h e work carries no date, but all the selections included carry prefaces by Liebig dated 1852. 46. F. L. Holmes, "Elementary Analysis a n d the Origin of Physiological Chemistry," Isis 54 (1963), 72-76. 47. J . Liebig, Familiar Letters on Chemistry in Its Relation to Physiology, Dietetics, Agriculture, Commerce and Political Economy. T h e work ran t h r o u g h many editions. T h a t cited here is the fourth English edition, edited by J o h n Blyth. London, Taylor, Walton and Maberly. 1859. 48. Ibid., p. 379. 49. Ibid., p. 343. 50. Ibid., p. 338. 51. Holmes, "Elementary Analysis," p. 75. 52. Liebig, Animal Chemistry, p. 34. 53. H. G. K. Westenbrink, "Biochemistry in Holland," Clio Medica 1 (1966), 153-159. 54. G. J. Mulder, "Zusammensetzung von Fibrin, Albumin, Leimzucker, Leucin u.s.w.," Liebigs Ann. 28 (1838), 73-82; Heber die Zusammensetzung einiger thierischen Substanzen," J. prakt. Chem. 16 (1839), 129-152. 55. Westenbrink, "Biochemistry," p. 154. 56. Liebig, Familiar Letters, p. 375. 57. Holmes, "Elementary Analysis," p. 75. 58. Η. B. Vickery, "Liebig a n d the Chemistry of Proteins," in Liebig and after Liebig, ed. F. R. Moulton, Washington, D.C., American Association f o r the Advancement of Science, 1942, p. 20. 59. Η. B. Vickery a n d C. L. A. Schmidt, " T h e History of the Discovery of the Amino Acids," Chem. Reviews 9 (1931), 174-188. 60. H. Braconnot, "Sur la conversion des matieres animales en nouvelle substance par le moyen d e l'acide sulfurique," Ann. chim. phys. [2] 13 (1820), 113-125.

260

Notes to Pages 1 7 4 - 1 8 0

61. Vickery and Schmidt, "Amino Acids," pp. 195-196. 62. J . Liebig, "Baldriansäure und ein neue Körper aus Käsestoff," LiebigsAnn. 62 (1847), 257-369. 63. J . Liebig, "Ueber die Bestandtheile der Flüssigkeiten des Fleisches, LiebigsAnn. 62 (1847), 257-369. 64. F. Bopp, "Einiges über Albumin, Casein, und Fibrin," Liebigs Ann. 6 9 (1849), 16-37. 65. Vickery and Schmidt, "Amino Acids," p. 209. 66. Vickery, "Liebig," p. 24. 67. Liebig, Familiar Letters, p. 391. 68. Vickery, "Liebig," p. 20. 69. Liebig, Familiar Letters, p. 409.

15. Enzymes and Cell Constituents 1. T h e work o f these men is reviewed by William Bulloch, The History of Bacteriology. London, Oxford University Press, 1938. pp. 47-52. 2. J . J . Berzelius, Rapport Anuel, Paris, 1843. p. 277. 3. E. Mitscherlich, "Ueber die chemische Zersetzung und Verbindung mittels Contactsubstanzen," Ann. phys. 55 (1842), 209-229. 4. R. J . Dubos, Louis Pasteur. Free Lance of Science. Boston, Little, Brown, 1950, p. 123. 5. [Wöhler and Liebig], "Das enträthselte Geheimniss der geistigen Gährung," Liebigs Ann. 29 (1839), 100-104. 6. Harold Finegold, " T h e Liebig-Pasteur Controversy," J. Chem. Educ. 31 (1954), 403-406. 7. L. Pasteur, "Memoire sur la fermentation appelee lactique," Ann. chim. phys. 52 (1858), 4 0 4 - 4 1 8 . Like his other papers, this has been reprinted in Oeuvres de Pasteur, reunies par Pasteur Vallery-Radot. Paris, Masson, 1922, vol. 2, pp. 3-13. This work will be cited in this chapter as Oeuvres. 8. L. Pasteur, "Animicules infusoires vivant sans gaz oxygene libre et de'terminant des fermentations," Com.pt. rend. 52 (1861), 344-347; Oeuvres, pp.. 136-138. 9. L. Pasteur, "Experiences et vues nouvelles sur la nature des fermentations," Compt. rend. 52 (1861), 1260-1264; Oeuvres, pp. 142-147. 10. L. Pasteur, "Recherches sur la putrefaction," Compt. rend. 56 (1863), 1189-1194; Oeuvres, p. 178. 1 1 . L . Pasteur, Studies on Fermentation. The Diseases of Beer, Their Causes, and the Means of Preventing Them, trans. Frank Faulkner and D. Constable Robb. New York, reprinted by American Library Service, 1945, p. 279. This is a translation of Pasteur's Etudes sur la biere, Paris, 1876. 12. Moritz Traube, " U e b e r das Verhalten der Alkoholhefe in sauerstoffgasfreien Medien," Ber. 7 (1874), 872-887.

Notes to Pages 180-184

261

13. Μ. Berthelot, "Sur la fermentation glucosique du sucre d e canne," Campt, rend. 50 (1860), 980-984. 14. L. Pasteur, "Note sur la fermentation alcoolique," Compt. rend. 50 (1860), 1083-1084; Oeuvres, pp. 127-128. 15. T h e discussion on both sides is reprinted in full in Oeuvres, pp. 586-615. 16. Oeuvres, p. 604. 17. Malcolm Dixon, " T h e History of Enzymes a n d Biological Oxidations," in The Chemistry of Life, ed. Joseph N e e d h a m . Cambridge, Cambridge University Press, 1970. p. 21. 18. Ibid., p. 17. 19. R. Kohler, " T h e background of E d u a r d Buchner's Discovery of Cell-Free F e r m e n t a t i o n , " / . Hist. Biol. 4 (1971), 35-61. 20. Dubos, Pasteur, pp. 201-202. 21. E d u a r d Buchner, "Alkoholische G ä r u n g o h n e Hefezellen," Ber 30 (1897), 117-124. 22. A r t h u r H a r d e n , Alcoholic Fermentation, 2nd ed. London, Longmans Green, 1914, p. 16. 23. G. Bertrand, "Sur l'interaction du manganese dans les oxydations provoquees par la laccase." Compt. rend. 124 (1897), 1032-1035. 24. A r t h u r H a r d e n and W. J. Young, " T h e Alcoholic Ferment of Yeast Juice," Proc. Roy. Soc. (London), series Β 77 (1905), 405-420; " T h e Alcoholic Ferment of Yeast Juice. II. T h e Co-ferment of Yeast Juice," Ibid., 78 (1906), 36y-375. 25. Dixon, "History of Enzymes," pp. 22-23. 26. R. Willstätter, "Problems a n d Methods in Enzyme Research,"/. Chem. Soc. (1927), 1359-1381. 27. J. B. S u m n e r , " T h e Isolation and Crystallization of the Enzyme Urease. Preliminary P a p e r , " / . Biol. Chem. 69 (1926), 435-441. 28. J. H. N o r t h r o p , "Crystalline Pepsin. I. Isolation a n d Tests of Purity,"/. Gen. Physiol. 13 (1930), 739-766. 29. J. H. N o r t h r o p , Crystalline Enzymes. New York, Columbia University Press, 1939, pp. 18-20. 30. L. Michaelis a n d Maud L. Menten, "Die Kinetik der Invertinwirkung," Biochem. Zeit. 49 (1913), 333-369; for f u r t h e r development of this formulation, see J . B. S. Haldane, Enzymes. London, Longmans Green, 1930. 31. H. Kiliani, "Ueber die Einwirkung von Blausäure auf Dextrose," Ber. 19 (1886), 767-772. 32. C. S. H u d s o n , "Emil Fischer's Discovery of the Configuration of Glucose,"/. Chem. Educ. 18 (1941), 353-359. 33. E. Fischer, "Ueber die Configuration des T r a u b e n z u c k e r u n d seiner Isomeren," Ber. 24 (1891), 1836-1845, 2683-2687. 34. W. Kühne, "Ueber die V e r d a u u n g d e r Eiweissstoffe durch d e n Pankreassaft," Virc.how's Arch. 39 (1867), 130-174.

262

Notes to Pages 184-187

35. W. K ü h n e , "Ueber das Trypsin," Verhandl. naturhist.-med. Verein zu Heidelberg 1 (1876), 194, 463. 36. R. H. Chittenden, The Development of Physiological Chemistry in the United States. American Chemical Society M o n o g r a p h no. 54, New York, Chemical Catalog Co., 1930, pp. 38-39. 37. W. Kühne a n d R. H. Chittenden, "Ueber die nächsten Spalt u n g s p r o d u k t e d e r Eiweisskorper," Zeit. Biol. 19 (1883), 159-208; "Ueber Albumosen," Zeit. Biol. 20 (1885), 11-51; Am. Chem. J. 6 (1884), 31-50; Globulin u n d Globuloses," Zeit. Biol. 22 (1886), 409-422; Trans. Conn. Acad. 7 (1885-1888), 207-219; "Ueber die Peptone," Zeit. Biol. 22 (1886), 423-458; Trans. Conn. Acad. 7 (1885-1888), 220-251; "Myosin u n d Myosinoses," Zeit. Biol. 25 (1888), 358-367, Trans. Conn. Acad. 7 (18851888), 139-147; "Ueber das N e u r o k e r a t i n , " ^ , Biol. 26 (1890), 291-323. 38. Η. B. Vickery and Τ . B. Osborne, "Α Review of Hypotheses of the Structure of Proteins," Physiol. Reviews 8 (1928), 393-446. 39. T h e o Curtius a n d F. Goedel, "Ueber Glycocolläther,"/. prakt. Chem. 37 (1888), 150-181. 40. E. Fischer, "Ueber die Hydrolyse des Caseins d u r c h Salzsäure," Zeit, physiol. Chem. 33 (1901), 151-176. 41. E. Fischer and E. Fourneau, "Ueber einige Derivate des Glycocolls," Ber. 34 (1901), 2868-2877. 42. E. Fischer, "Ueber einige Derivate des Glycocolls, Alanins, u n d Leucins," Ber. 35 (1902), 1095-1106. 43. E. Fischer, "Synthese von Derivaten der Polypeptide," Ber. 36 (1903), 2094-2106. 44. F. Hofmeister, "Ueber Bau u n d G r u p p i e r u n g d e r Eiweisskorper," Ergebnisse der Physiologie 1 (1902), 792. 45. E. Fischer, "Proteine u n d Polypeptide," Zeit, angew. Chem. 20 (1907), 913-917. 46. F. Miescher, "Ueber die chemische Zusammensetzung des Eiterzellen," Hoppe-Seylers Med.-Chem. Untersuchungen (1871), 441; F. H o p p e Seyler, "Ueber die chemische Zusammensetzung des Eiters, Ibid., 486. 47. J. Piccard, "Ueber Protamine, Guanin u n d Sarkin, als Bestandtheile des Lachssperma," Ber. 7 (1874), 1714-1719. 48. A. Kossei, "Ueber das Nuclein d e r Hefe," Zeit, physiol. Chem. 3 (1879), 284-291. 49. A. Kossei, "Ueber Xanthin u n d Hypoxanthin," Zeit, physiol. Chem. 6 (1882), 422-431. 50. A. Kossei, "Weitere Beiträge zur Chemie des Zellkerns," Zeit, physiol. Chem. 10 (1886), 248-264. 51. R. Altmann, "Ueber Nucleinsäuren," Arch Anat. Physiol., Physiol. Abt. (1889), 524-536. 52. A. Kossei and A. N e u m a n n , "Ueber das T h y m i n , ein Spaltungsproduct d e r Nucleinsäure," Ber. 26 (1893), 2753-2756. 53. A. Kossei a n d A. N e u m a n n , "Darstellung u n d Spaltungsproducte d e r Nucleinsäure, Ber. 27 (1894), 2215-2222.

Notes to Pages 187-191

263

54. Alberto Ascoli, "Ueber ein neues Spaltungsproduct des H e f e n u cleins," Zeit, physiol. Chem. 31 (1900-1901), 161-164. 55. Walter Jones, Nucleic Acids. Their Chemical Properties and Physiological Conduct. London, Longmans Green, 1914, pp. 9-12. 56. P. A. Levene a n d J. A. Mandel, "Ueber die Konstitution d e r Thymo-nucleinsäure," Ber. 41 (1908), 1905-1909. 57. P. A. Levene and W. A. Jacobs, "Ueber die Hefe-nucleinsäure," Ber. 42 (1909), 2474-2476. 58. P. A. Levene and W. A. Jacobs, "On the Structure of T h y m u s Nucleic A c i d , " / . Biol. Chem. 12 (1912), 411-420. 59. P. A. Levene and E. S. London, "Guanine Desoxypentoside f r o m T h y m u s Nucleic A c i d , " / . Biol. Chem. 81 (1929), 711-712. 60. P. A. Levene, L. A. Mikeska, a n d T . Mori, " T h e Carbohydrate of Thymonucleic A c i d , " / . Biol. Chem. 85 (1930), 785-787. 61. Einar H a m m a r s t e n , "Zur Kentnis der biologischen B e d e u t u n g der Nucleinsäureverbindungen," Biochem. Zeit. 144 (1924), 383-466. 62. G e r h a r d Schmidt, E. G. Pickels, and P. A. Levene, "Enzymatic Dephosphorylation of Desoxyribonucleic Acids of Various Degrees of Polymerization,"/. Biol. Chem. 127 (1939), 251-259. 63. W. M. Stanley, "Isolation of a Crystalline Protein Possessing the Properties of Tobacco-mosaic Virus," Science 81 (1935), 644-645. 64. F. C. Bawden and N. W. Pirie, " T h e Isolation and Some Properties of Liquid Crystalline Substances f r o m Solanaceous Plants Infected with T h r e e Strains of Tobacco Mosaic Virus," Proc. Roy. Soc. (London), series B, 123 (1937), 274-320.

16 Energy Production and Biological Oxidations 1 . A full account of these developments is given by C. A. Culotta, "Tissue Oxidation and Theoretical Physiology: B e r n a r d , Ludwig a n d Pflüger," Bull. Hist. Med. 44 (1970), 109-140. 2. Gustav Magnus, "Ueber die im Blute erhaltenen Gase, Sauerstoff, Stickstoff u n d Kohlensäure," Poggendorfs Ann. Phys. Chem. 40 (1837), 583606. 3. E. Farber, " T h e Color of Venous Blood," Isis 45 (1954), 3-9; George Rosen, " T h e Conservation of Energy a n d the Study of Metabolism," in The Historical Development of Physiological Thought, ed. C. M. C. Brooke a n d P. F. Cranefield. New York, H a f n e r , 1959, pp. 243-263. 4. J . R. Mayer, " B e m e r k u n g e n über die Kräfte der unbelebten Natur," Liebigs Ann. 42 (1842), 233-249. A facsimile reproduction of the p a p e r with English translation is given by G. Sarton, " T h e Discovery of the Law of Conservation of Energy," Isis 13 (1929), 18-34. 5. Μ. von Pettenkoffer a n d C. Voit, " U n t e r s u c h u n g e n über den Stoffverbrauch des normalen Menschen," Zeit. Biol. 2 (1866), 507. 6. H. Helmholtz, Ueber die Erhältung der Kraft. Berlin, G. Reimer, 1847.

264

Notes to Pages 1 9 1 - 1 9 5

7. J . Β. Boussingault, "Analyses comparees des Alimens consommes et des produits rendus par une vache lactiere; recherches entreprises dans le but d'examiner si les animaux herbivores empruntent l'azote ä l'atmosphere." Ann. chim. phys. [2] 71 (1839), 113-127. 8. R. P. Aulie, "Boussingault and the Nitrogen Cycle," Proc. Am. Philosoph. Soc. 114 (1970), 435-479. 9. Rosen, "Conservation o f Energy," p. 258. 10. V. Regnault and J . Reiset, "Recherches chimiques sur la respiration des animaux des diverses classes," Ann. chim. phys. [3] 26 (1849), 299-519; a German translation o f the paper appears in Liebigs Ann. 73 (1850), 92123, 129-179, 257-321. 11. Carl Voit, "Untersuchungen über die Ausscheidungswege der stickstoffhaltigen Zersetzungs-Produkte aus dem thierischen Organismus," Zeit. Biol. 2 (1866), 39. 12. G. Lusk, The Elements of the Science of Nutrition. 4th ed., Philadelphia, Saunders, 1928. p. 24. 13. Pettenkoffer and Voit. "Stoffverbrauch." 14. C. Voit, "Max von Pettenkoffer dem Physiologen, zum Gedächtnis," Zeit. Biol. 41 (1901), V I I . 15. Ε. Pflüger, "Nachtrag zu Dr. G. Colasanti's in diesem Archiv enthaltenen Abhandlung," Pflügers Arch, gesamt. Physiol. 14 (1877), 469472. 16. Ε. Pflüger, "Neue Einwände des Herrn Professor H. Senator gegen die Anpassung der Wärmeproduction an den Wärmeverlust bei Wärmeblutern," Pflügers Arch, gesamt. Physiol. 15 (1877), 104-115. 17. Μ. Rubner, "Die Quelle der thierischen Wärme," Zeit. Biol. 30 (1894), 73-142. 18. M. Rubner, "Beiträge zur Lehre vom Kraftwechsel," Sitzber. Bayer. Akad., Math. phys. Classe 15 (1885), 454-455. 19. Lusk, Nutrition, p. 36. 20. D. Keilin, The History of Cell Respiration and Cytochrome. Cambridge, Cambridge University Press, 1966, pp. 34-36. 21. Georg Liebig, "Ueber die Respiration der Muskeln," Arch. Anat. Physiol. Wissensch. Med. (1850), 393-416. 22. M. T r a u b e , "Ueber die Beziehung der Respiration zur Muskelthätigkeit und die Bedeutung der Respiration überhaupt," Virchow's Arch. 21 (1861), 386-414. 23. Ε. Pflüger, "Ueber die Diffusion des Sauerstoffs, dem Ort und die Gesitze der Oxydationsprocesse in theirischen Organismus." Pflügers Arch, gesamt. Physiol. 6 (1872), 43-64. 24. Ε. Pflüger, "Beiträge zum Lehre von der Respiration. I. Ueber die physiologische Verbrennung in den lebendigen Organismus," Pflügers Arch, gesamt. Physiol. 10 (1875), 251-367. 25. C. A. Culotta, " O n the Color of the Blood from Lavoisier to Hoppe-Seyler, 1777-1864. A Theoretical Discussion," Episteme 4 (1970), 219-233.

Notes to Pages 195-199

265

26. Ε. B a u m a n n a n d Α. Kossei, "Felix Hoppe-Seyler," Ber. 28 (1896), 1151 R. 27. F. H o p p e , " U e b e r das V e r h a l t e n des B l u t f a r b s t o f f e s im S p e c t r u m des Sonnenlichts," Virchows Arch. 23 (1862), 446-449. 28. Felix Hoppe-Seyler, " U e b e r die c h e m i s c h e n u n d optischen E i g e n s c h a f t e n des Blutfarbstoffs," Virchows Arch. 29 (1864), 233-235. 29. G. G. Stokes, " O n t h e Reduction a n d Oxidation of t h e C o l o u r i n g Matter of Blood," Proc. Roy. Soc. (London) 13 (1864), 355-364. 30. William Küster, " U e b e r die Konstitution d e s H ä m i n s , " Zeit, physiol. Chem. 88 (1913), 377-388. 31. H a n s Fischer, " U b e r P o r p h y r i n e u n d i h r e Synthesen," Ber. 60 (1927), 2611-2651. 32. C. F. Schönbein, " B e o b a c h u n g e n ü b e r d e n bei d e r Electrolysation des Wassers u n d d e m A u s s t r ö m e n d e r gewöhnlichen Electricität a u s Spitzen sich entwickelnden G e r u c h , " Poggendorfs Ann. Phys. 50 (1840), 616-635. 33. E. F a r b e r , " I n d u c e d O x i d a t i o n - R e d u c t i o n Processes," Chymia 10 (1965), 135. 34. Schönbein, " O n O z o n e a n d Ozonic Activity in M u s h r o o m s , " Phil. Mag. [4] 11 (1856), 137-141. 35. Moritz T r a u b e , "Zur T h e o r i e d e r G ä h r u n g s - u n d V e r w e s u n g s e r s c h e i n u n g e n , wie d e r F e r m e n t w i r k u n g e n ü b e r h a u p t , " Ann. phys. Chem. 103 (1858), 331-344. 36. F. Hoppe-Seyler, " E r r e g u n g des S a u e r s t o f f s d u r c h n a s c i r e n d e n Wasserstoff," Ber. 12 (1879), 1551-1555. 37. T h e full story of M a c M u n n ' s work is given in Keilin, Cytochrome (see n. 20 above), p p . 86-116. 38. O t t o W a r b u r g , " U b e r Eisen, d e n s a u e r s t o f f - ü b e r t r ä g e n d e n Bestandteil d e s A t m u n g s f e r m e n t s , " Ber. 58 (1925), 1001-1011. 39. O t t o W a r b u r g , " T h e E n z y m e Problem a n d Biological O x i d a t i o n , " Johns Hopkins Hosp. Bull. 46 (1930), 341-358. 40. H e i n r i c h Wieland, " U b e r d e n M e c h a n i s m u s d e r Oxydationsvorgänge," Ber. 46 (1913), 3327-3342. 41. T . T h u n b e r g , " T h e Hydrogen-Activating Enzymes of t h e Cells," Quart. Rev. Biol. 5 (1930), 318-347. 42. D. Keilin, " O n C y t o c h r o m e , a Respiratory Pigment, C o m m o n to Animals, Yeast, a n d H i g h e r Plants," Proc. Roy. Soc., series B, 98 (1925), 312-339. 43. D. Keilin, " C y t o c h r o m e a n d Respiratory Systems," Proc. Roy. Soc., series B, 104 (1929), 206-252. 44. O t t o W a r b u r g a n d W a l t e r Christian, " U b e r das gelbe F e r m e n t u n d seine W i r k u n g e n , " Biochem. Zeit. 266 (1933), 377-411. 45. O t t o W a r b u r g a n d Walter Christian, " C o - F e r m e n t p r o b l e m , " Biochem. Zeit. 275 (1935), 464. 46. O t t o W a r b u r g , Walter Christian, a n d A l f r e d Griese, "Wasserstoffuberträgendes Co-Ferment, seine Zusammensetzung und Wirkungsweise," Biochem. Zeit. 282 (1935), 157-205.

266

Notes to Pages 200-204

47. Albert Szent-Györgyi, On Oxidation, Fermentation, Vitamins, and Disease, Baltimore, Williams a n d Wilkins, 1939, p. 46.

Health

17 Intermediary Metabolism 1 . T . S. Hall, Ideas of Life and Matter. Chicago, University of Chicago Press, 1969, vol. 2, pp. 351-353. 2. F. Gowland Hopkins, "Some Oxidation Mechanisms of the Cell," Johns Hopkins Hosp. Bull. 32 (1921), 322. 3. A r t h u r H a r d e n a n d W. J . Young, " T h e Alcoholic Fermentation of Yeast Juice," Proc. Roy. Soc. (London), series Β, 77 (1905), 405-420. 4. A r t h u r H a r d e n and W. J. Young, " T h e Alcoholic Fermentation of Yeast Juice. Part III. T h e Function of Phosphates in the Fermentation of Glucose by Yeast Juice," Proc. Roy. Soc. (London), series B, 80 (1908), 299-311. 5. A r t h u r H a r d e n , Alcoholic Fermentation. 2nd ed. London, L o n g m a n s Green, 1914, p. 49. 6. W. M. Fletcher and F. Gowland Hopkins, "Lactic Acid in Amphibian Muscle,"/. Physiol. 35 (1907), 247-309. 7. G. E m b d e n , K. Baldes, a n d E. Schmitz, "Über d e n Chemismus d e r Milchsäurebildung aus T r a u b e n z u c k e r im Tierkörper," Biochem. Zeit. 45 (1912), 108-133. For a full treatment of the development of muscle biochemistry see Dorothy N e e d h a m , Machina Carnis: The Biochemistry of Muscular Contraction in its Historical Development. Cambridge, Cambridge University Press, 1971. 8. O. Meyerhof, "Über die E n e r g i e u m w a n d l u n g e n im Muskel. II. Das Schicksal d e r Milchsäure in d e r Erholungsperiode des Muskels," Arch, ges. Physiol. 182 (1920), 284-317. 9. G. E m b d e n and F. Laquer, "Über die Chemie des Lactocidogens. 1. Isolierungsversuche," Zeit, physiol. Chem. 93 (1914), 94-123. 10. G. E m b d e n and F. Laquer, "Uber die Chemie des Lacticidogens. II," Zeit, physiol. Chem. 98 (1917), 181. 11. Carl Neuberg, " Ü b e r f u h r u n g der Fructose-diphosphorsäure in Fructose-monophosphorsäure," Biochem. Zdt. 88 (1918), 432-456. 12. R. Robison, "A New Phosphoric Ester Produced by the Action of Yeast Juice on Hexoses "Biochem. J. 16 (1922), 809-824. 13. C. F. Cori and G. Cori, "Mechanism of Formation of Hexo s e m o n o p h o s p h a t e in Muscle a n d Isolation of a New Phosphate Ester," Proc. Soc. Exper. Biol. Med. 34 (1936), 702-705. 14. Otto Meyerhof, "Die Energieumwandlung im Muskel. III. Kohle n h y d r a t u n d Milchsäuremsatz im Froschmuskel," Arch. ges. Physiol. 185 (1920), 211-232. 15. O. Meyerhof, Chemical Dynamics of Life Phaenomena. Philadelphia, Lippincott, 1924, pp. 41-60. 16. Ibid., p. 58.

Notes to Pages 204-206

267

17. Philip Eggleton and Grace Palmer Eggleton, " T h e Inorganic Phosphate and a Labile Form o f Organic Phosphate in the Gastrocnemius o f the Frog," Biochem. J. 21 (1927), 190-195. 18. Cyrus H. Fiske and Y. Subbarow, " T h e Nature of the 'Inorganic Phosphate' in Voluntary Muscle," Science 6 5 (1927), 401-403. 19. Cyrus H. Fiske and Y. Subbarow, "Phosphocreatine,"/. Biol. Chem. 81 (1929), 629-679. 20. K. Lohmann, "Uber die Pyrophosphatfraktion im Muskel," Naturwissensch. 17 (1929), 624-625. 21. Cyrus Η. Fiske and Y. Subbarow, "Phosphorus Compounds o f Muscle and Liver," Science 70 (1929), 381-382. 22. O. Meyerhof, " T h e Isolation o f Glycolytic Enzyme from the Muscle and the Mechanism o f Lactic Acid Formation in Solution," Naturwissensch. 14 (1926), 1175-1180. 23. G. Embden, H. J . Deuticke, and G. Kraft, "Über die intermediären Vorgänge bei der Glykolyse in der Muskulatur," Klin. Wochensch. 12 (1933), 213-215. 24. O. Meyerhof, "Intermediate Carboyhydrate Metabolism" in Α Symposium on Respiratory Enzymes, Madison, Wis., University o f Wisconsin Press, 1942, pp. 3-15. 25. O. Meyerhof, "New Investigations on Enzymatic Glycogen and Phosphorylation," Experientia 4 (1948), 169-176. 26. F. Lipmann, "Metabolic Generation and Utilization of Phosphate Bond Energy," Advances in Enzymology 1 (1941), 99-162. 27. B. Gözsy and A. Szent-Györgyi, "Uber den Mechanismus der Hauptatmung des Taubenbrustmuskels," Zeit, physiol. Chem. 224 (1934), 1-10.

28. A. Szent-Györgyi, " U b e r die Bedeutung der Fumarsäure für die tierische Gewebsatmung. Einleitung, Übersicht, Methoden," Zeit, physiol. Chem. 2 3 6 (1935), 1-20; 244 (1936), 105-116. 29. F. J . Stare and C. A. Baumann, " T h e Effect o f Fumarate on Respiration," Proc. Roy. Soc. (London), series Β, 121 (1936), 338-357. 30. Κ. Laki, F. Β. Straub, and A. Szent-Gyorgyi, "Über die Atmungskatalyse durch C4-Dicarbonsäuren," Zeit, physiol. Chem. 247 (1937), I - I I . 31. C. Martius and F. Knoop, "Die physiologischen Abbau der Citronensäure," Zeit, physiol. Chem. 2 4 6 (1937), I - I I . 32. Carl Martius, "Über den Abbau der Citronensaure," Zeit, physiol. Chem. 247 (1937), 104-110. 33. Η. A. Krebs, " T h e History of the Tricarboxylic Acid Cycle," Perpectives Biol. Med. 14 (1970), 154-170. 34. H. Krebs and W. A. Johnson, " T h e Role o f Citric Acid in Intermediate Metabolism in Animal Tissues," Enzymologia 4 (1937), 148-156. 35. H. A. Krebs and Kurt Henseleit, "Untersuchungen über die Harnstoffbildung im Tierkörper," Zeit, physiol. Chem. 2 1 0 (1923), 33-66. 36. Krebs, "Tricarboxylic Cycle."

268

Notes to Pages 2 0 6 - 2 0 9

37. F. L i p m a n n , "Acetylation of Sulfanilamide by Liver H o m o g e n a t e s a n d E x t r a c t s , " / . Biol. Chem. 160 (1945) 173-190. 38. Fritz L i p m a n n , N a t h a n O. Kaplan, G. David Novelli, L. Constance T u t t l e , a n d Beverly M. G u i r a r d , " C o e n z y m e f o r Acetylation, a Pantothenic Acid D e r i v a t i v e , " / . Biol. Chem. 167 (1947), 869-870. 39. F e o d o r Lynen, Ernestine Reichert, a n d L u i s t r a u d R u e f f , "Zum biologischen Abbau d e r Essigsäure. VI. 'Aktivierte Essigsäure,' ihre Isolierung aus H e f e u n d ihre chemische N a t u r , " Liebigs Ann. 574 (1951), 1-32. 40. F r a n z K n o o p , " D e r Abbau a r o m a t i s c h e r F e t t s ä u r e n im T i e r k ö r p e r , " Beiträge Chem. Physiol. Path. 6 (1905), 150-162. 41. R u d o l f S c h o e n h e i m e r a n d D. Rittenberg, " D e u t e r i u m as a n I n d i c a t o r in t h e Study of I n t e r m e d i a r y Metabolism. I I I . T h e Role of Fat T i s s u e s , " / . Biol. Chem. III. (1935), 175-181. 42. O t t o Folin, "A T h e o r y of Protein Metabolism," Am. J. Physiol. 13 (1905), 117-138. 43. G e o r g e Hevesy, " T h e A b s o r p t i o n a n d T r a n s l o c a t i o n of Lead by Plants. A C o n t r i b u t i o n to the Application of the M e t h o d of Radioactive Indicators in the Investigation of t h e C h a n g e of Substances in Plants," Biochem.J. 17 (1923), 439-445. 44. O. Chiewitz a n d G. Hevesy, "Radioactive Indicators in t h e Study of P h o s p h o r u s Metabolism in Rats "Nature 136 (1935), 754-755. 45. Η . B. Vickery a n d Τ . B. O s b o r n e , "A Review of H y p o t h e s e s of the S t r u c t u r e of Proteins," Physiol. Reviews 8 (1928), 393-446. 46. G. B r e d i g , "Beiträge zur Stöchiometrie d e r Ionenbeweglichkeit," Zeit, physik. Chem. 13 (1894), 323. 47. F. W. Küster, "Kritische Studien zur volumetrischen B e s t i m m u n g von c a r b o n h a l t i g e n Alkalilaugen u n d von Alkalicarbonaten, sowie ü b e r das V e r h a l t e n von P h e n o l p h t h a l e i n u n d M e t h y l o r a n g e als I n d i k a t o r e n , " Zeit, anorg. Chem. 13 (1897), 127-150. 48. G. Bredig, " U b e r a m p h o t e r e Elektrolyte u n d i n n e r e Salze," Zeit. Elektrochem. 6 (1899), 33-36. 49. Elliot Quincy A d a m s , "Relations b e t w e e n the Constants of Dibasic Acids a n d of A m p h o t e r i c Electrolytes,"/. Am. Chem. Soc. 38 (1916), 15031510. 50. Niels B j e r r u m , "Die Konstitution d e r A m p h o l y t e , b e s o n d e r s d e r A m i n o s ä u r e n , u n d ihre Dissoziationkonstanten," Zeit, physik. Chem. 104 (1923), 147-173. 51. W. B. H a r d y , " O n t h e Coagulation of Proteid by E l e c t r i c i t y , " / . Physiol. 24 (1899), 288-304. 52. W. B. H a r d y , "A Preliminary Investigation of the Conditions which D e t e r m i n e t h e Stability of Irreversible Hydrosols," Proc. Roy. Soc. London 66 (1900), 110-125. 53. W. B. H a r d y , "Colloidal Solution. T h e Globulins," / . Physiol. 33 (1905), 251-337.

Notes to Pages 210-215

269

54. S. P. L. Sörensen, "Enzymstudien. II. Uber die Messung u n d die B e d e u t u n g d e r Wasserstoffionenkonzentration bei enzymatischen Prozessen," Biochem. Zeit. 21 (1909), 131-200. 55. Jacques Loeb, Proteins and the Theory of Colloidal Behavior. New York, McGraw Hill, 1922. 56. Edwin J. Cohn and J o h n T . Edsall, Proteins, Amino Acids, and Peptides as Ions and Dipolar Ions. New York, Reinhold, 1943. 57. A r n e Tiselius, "A New Apparatus for Electrophoretic Analysis of Colloidal Mixtures," Trans. Faraday Soc. 33 (1937), 524-531. 58. T h e Svedberg, "Sedimentation of Molecules in Centrifugal Fields." Chem. Reviews. 14 (1934), 1-15. 59. M. Tswett, "Physikalisch-chemische Studien über das Chlorophyll. Die Adsorptionen," Ber. deutsch, botanisch. Gesell. 24 (1906), 316-323. 60. F. Sanger, " T h e Structure of Insulin" in Currents in Biochemical Research 1956, ed. David E. Green. New York, Interscience, 1956, pp. 434-459. 61. J o h n C. Kendrew, "Myoglobin and the Structure of Proteins," Science 139 (1963), 1259-1266. 62. Μ. F. Perutz, "X-ray Analysis of Hemoglobin," Science 140 (1963), 863-869. 63. Α. Ε. Garrod, Inborn Errors of Metabolism. London, O x f o r d University Press 1963. Reprinted f r o m the original L o n d o n edition of 1909.

18

Vitamins

1. Quoted in H. C. S h e r m a n and S. L. Smith, The Vitamins. 2nd ed. New York, Chemical Catalog Co. 1931, p. 14. 2. Aaron J. I h d e a n d Stanley L. Becker, "Conflict of Concepts in Early Vitamin Studies,"/. Hist. Biol. 4 (1971), 1-33. 3. N. Lunin, "Ueber die B e d e u t u n g d e r anorganischen Salze f ü r die E r n ä h r u n g des Thiers," Zeit, physiol. Chem. 5 (1881), 31-39. 4. T h e results were first published in the Sei-I-Kai Medical Journal, but a review of those obtained between 1878 and 1886 was published in T h e Lancet 2 (1887), 189-190; see also The Lancet 1 (1906), 1369-1374. 5. Q u o t e d by L. J. Harris, Vitamins in Theory and Practice, 4th ed. Cambridge, Cambridge University Press, 1955, p. 16. 6. Τ. B. Osborne a n d L. B. Mendel, " T h e Role of Different Proteins in Nutrition a n d Growth," Science 34 (1911), 722-733. 7. Wilhelm Stepp, "Versuche über F ü t t e r u n g mit lipoidfreier Nahrung," Biochem. Zeit. 22 (1909), 452-460. 8. F. Gowland Hopkins, "Feeding Experiments Illustrating the I m p o r tance of Accessory Factors in Normal Dietaries,"/. Physiol. 44 (1912), 425. 9. C. Eijkman, "Eine Beri Beri-ahnliche Krankheit d e r H ü h n e n , " Virchows Arch. 148 (1897), 523-532. 10. Harris, Vitamins, p. 8.

270

Notes to Pages 215-219

11. C. Eijkman, "Uber Ernährungspolyneuritis," Arch. Hyg. 58 (1906), 150-170. 12. C. Funk, " T h e Substance f r o m Yeast a n d Certain Foodstuffs Which Prevents Polyneuritis (Beri Ben)," Brit. Med. J. 1912, 787-788. 13. J. C. D r u m m o n d a n d C. Funk, " T h e Chemical Investigation of the Phosphotungstate Precipitate f r o m Rice Polishings," Biochem. J. 8 (1914), 598-615. 14. A. Hoist, "Experimental Studies Relating to 'Ship Beri Beri' a n d Scurvy,"/. Hyg. 7 (1907), 619-633. 15. A. Hoist a n d T . Frölich, "On the Etiology of S c u r v y , " / . Hyg. 7 (1907), 634-671. 16. Casimir Funk, " T h e Etiology of the Deficiency Diseases. Beri-beri, Polyneuritis in Birds, Epidemic Dropsy, Scurvy, Experimental Scurvy in Animals, Infantile Scurvy, Ship Beri-beri, Pellagra," J. State Med. 20 (1912), 341-368. 17. Ε. V. McCollum a n d Marguerite Davis, " T h e Necessity of Certain Lipins in the Diet d u r i n g G r o w t h . " / . Biol. Chem. 15 (1913), 167-175. 18. Τ. B. Osborne a n d L. B. Mendel, " T h e Influence of Butter Fat on G r o w t h , " / . Biol. Chem. 16 (1913), 423-437. 19. Ε. V. McCollum a n d Marguerite Davis, " T h e N a t u r e of t h e Dietary Deficiencies of Rice,"/. Biol. Chem. 23 (1915), 181-230. 20. Ε. V. McCollum a n d Marguerite Davis, " T h e Essential Factors in the Diet During G r o w t h , " / . Biol. Chem. 23 (1915), 231-246. 21. Ε. V. McCollum a n d Cornelia Kennedy, " T h e Dietary Factors Operating in the Production of Polyneuritis,"/. Biol. Chem. 24 (1916), 491-502. 22. Jack Cecil D r u m m o n d , " T h e Nomenclature of the So-Called Accessory Food Factors (Vitamins)," Biochem. J. 14 (1920), 660. 23. Ε. V. McCollum, Nina Simmonds, a n d J. Ernestine Becker, "Studies on Experimental Rickets. XXI. An Experimental Demonstration of the Existence of a Vitamin Which Promotes Calcium Deposition," / . Biol. Chem. 53 (1922), 293-312. 24. H. Steenbock a n d A. Black, "Fat Soluble Vitamins. X V I I . T h e Induction of Growth Promoting a n d Calcifying Properties in a Ration by Exposure to Ultra-Violet L i g h t , " / . Biol. Chem. 61 (1924), 405-422. 25. Alfred F. Hess a n d Mildred Weinstock, "Antirachitic Properties I m p a r t e d to I n e r t Fluids and to Green Vegetables by Ultra-Violet I r r a d i a t i o n , " / . Biol. Chem. 62 (1924), 301-313. 26. Alfred F. Hess and Mildred Weinstock, " T h e Antirachitic Value of Irradiated Cholesterol a n d Phytosterol. II. F u r t h e r Evidence of C h a n g e in Biological Activity,"/. Biol. Chem. 64 (1925), 181-191. 27. Alfred F. Hess a n d A. Windaus, "Contaminating Substances as a Factor in the Activation of Cholesterol by Irradiation," Proc. Soc. Exper. Biol. Med. 24 (1927), 369-370.

Notes to Pages 219-221

271

28. A l f r e d F. Hess a n d Α. W i n d a u s , " T h e D e v e l o p m e n t o f M a r k e d Activity in E r g o s t e r o l Following Ultra-Violet I r r a d i a t i o n , " Proc. Soc. Exper. Biol. Med. 24 (1927), 4 6 1 - 4 6 2 . 29. J . W a d d e l l , " T h e P r o v i t a m i n D of Cholesterol. I. T h e Antirachitic Efficiency of I r r a d i a t e d Cholesterol , " / . Biol. Chem. 105 (1934), 7 1 1 - 7 3 9 30. A. W i n d a u s , Η . Littre', a n d Fr. S c h e n k , " Ü b e r d a s 7D e h y d r o - C h o l e s t e r i n , " Liebigs Ann. 5 2 0 (1935), 98-106. 31. J . G o l d b e r g e r , G. A. W h e e l e r , R. D. Lillie, a n d L. M. Rogers, "A F u r t h e r S t u d y of B u t t e r , Fresh B e e f , a n d Yeast as Pellagra-Preventives, with C o n s i d e r a t i o n of t h e Relation of Factor P-P of Pellagra (and Black T o n g u e in Dogs) to V i t a m i n B," U. S. Pub. Health Reports 41 (1926), 297318. 32. H e n r i e t t e Chick a n d M a r g a r e t H o n o r a Roscoe, " O n t h e C o m p o s i t e N a t u r e of t h e W a t e r Soluble Β V i t a m i n , " Biochem. J. 21 (1927), 698-711. 33. R. K u h n , P. György, a n d T . W a g n e r - J a u r e g g , " U b e r O v o f l a v i n , d e n F a r b s t o f f des Eiklars," Ber. 6 6 B (1933), 576-580. 34. Paul György, " V i t a m i n B2 a n d t h e Pellagra-like D e r m a t i t i s in Rats," Nature 133 (1934), 498-499. 35. T . W. Birch, P. György, a n d L. J . H a r r i s , " T h e V i t a m i n B2 C o m plex. D i f f e r e n t i a t i o n of t h e A n t i - B l a c k t o n g u e a n d t h e P. P. Factors f r o m Lactoflavin a n d V i t a m i n Be (So-Called R a t Pellagra Factor')," Biochem. J. 2 9 (1935), 2 8 3 0 - 2 8 5 0 . 36. C. A. E l v e h j e m , R. J . M a d d e n , F. M. S t r o n g , a n d D. W. Wooley, "Relation of Nicotinic Acid a n d Nicotinic Acid A m i d e to C a n i n e Black T o n g u e , " / . Am. Chem. Soc. 5 9 (1937), 1767-1768. 37. Η . M. Evans a n d K. S. B i s h o p , " O n t h e Existence of a H i t h e r t o U n r e c o g n i z e d Dietery Factor Essential f o r R e p r o d u c t i o n , " Science 56 (1922), 650-651. 38. H . D a m , " T h e A n t i h a e m o r r h a g i c V i t a m i n of t h e Chick," Nature 135 (1935), 652-653. 39. H . S t e e n b o c k , " W h i t e C o r n vs Yellow C o r n a n d a P r o b a b l e Relation b e t w e e n t h e Fat Soluble V i t a m i n e a n d Yellow Plant P i g m e n t s , " Science 5 0 (1919), 352-353. 40. J . C. D r u m m o n d , " R e s e a r c h e s o n t h e Fat Soluble Accessory Substance. I. O b s e r v a t i o n s u p o n Its N a t u r e a n d P r o p e r t i e s , " Biochem. J. 13 (1919), 81-94. 41. J . C. D r u m m o n d , H . J . C h a n n o n , a n d {Catherine H o p e C o w a r d , "Studies o n t h e C h e m i c a l N a t u r e of V i t a m i n A," Biochem. J. 19 (1925), 1047-1067. 42. B e t h v o n E u l e r , H a n s v o n E u l e r , a n d H a r r y H e l l s t r ö m , " A - V i t a m i n W i r k u n g e n d e r L i p o c h r o m e , " Biochem. Zeit. 2 0 3 (1928), 370-384. 43. P. K a r r e r , A. H e l f e n s t e i n , Η . W e h r l i , a n d Α. Wettstein, " P f l a n z e n f a r b s t o f f e . X X V . " U b e r d i e K o n s t i t u t i o n d e s Lycopins u n d C a r o t i n s , " Helv. Chim. Acta 13 (1930). 1084-1099; P. K a r r e r , A. H e l f e n s t e i n , H .

272

Notes to Pages 221-225

Wehrli, Β. Pieper, and R. Morf, "Pflanzenfarbstoffe. XXX. Beiträge zur Kenntnis des Carotins, d e r Xanthophylle, des Fucoxanthins u n d Capsanthins," Helv. Chim. Acta 14 (1931), 614-632. 44. Paul Karrer, " T h e Chemistry of Vitamins A a n d C," Chem. Reviews 14 (1934), 17-30. 45. Albert Szent-Györgyi, "Observations on the Functions of Peroxidase Systems a n d the Chemistry of the Adrenal Cortex. Description of a New Carbohydrate Derivative," Biochem. J. 22 (1928), 1387-1409. 46. J. L. Svirbeli and A. Szent-Györgyi, " T h e Chemical Nature of Vitamin C," Biochem. J. 27 (1933), 279-285. 47. A. Szent-Györgyi and W. N. Haworth, "Hexuronic Acid (Ascorbic Acid) as the Antiscorbutic Factor," Nature 131 (1933), 24. 48. T. Reichstein, Α. Grüssner, a n d R. O p p e n a u e r , "Synthese d e r du n d / - A s c o r b i n s ä u r e (C-Vitamin)," Helv. Chim. Acta 16 (1933), 1019-1033. 49. R. G. Ault et al., "Synthesis of d- a n d /-Ascorbic Acid a n d of Analogous Substances,"/. Chem. Soc. 1933, 1419-1423. 50. W. N. Haworth, E. L. Hirst, a n d S. S. Zilva, "Physiological Activity of Synthetic Ascorbic A c i d , " / . Chem. Soc. 1934, 1155-1156.

19 Hormones 1. T h e history of hormones is given in detail in H. D. Rolleston, The Endocrine Organs in Health and Disease with an Historical Review. London, O x f o r d University Press, 1936. A shorter account is given by F. G. Young, " T h e Evolution of Ideas about Animal H o r m o n e s " in The Chemistry of Life, ed. Joseph N e e d h a m . Cambridge University Press, 1970, pp. 125-155. 2. F. G. Hopkins, "Introduction," Ergebnisse Vitamin Hormonforsch, 1 (1938), v. 3. Rolleston, Endocrine Organs, pp. 1-22. 4. A. A. Berthold, "Transplantation der H o d e n , " Arch. Anat. Physiol. Wissensch. Med. 1849, 42-46. 5. C. B e r n a r d , Recherches sur une nouvelle fonction du foie. Paris, Bailliere, 1853, p. 54. 6. Rolleston, Endocrine Organs, p. 340. 7. C. E. Brown-Sequard, "Recherches expe'rimentales sur la physiologie et la pathologie des capsules surrenales," Compt. rend. 43 (1856), 422-425. C. E. Brown-Se'quard, "Recherches experimentales sur la physiologie des capsules surrenales," Compt. rend. 43 (1856), 542-546. 8. "Meeting of the Clinical Society of London, November 23, 1883," Brit. Med. J. 2 (1883), 1072-1074. 9. Victor Horsley, "On the Function of the Thyroid Gland," Proc. Roy. Soc. London 38 (1884), 5-7.

Notes to Pages 225-227

273

10. Μ. Schiff, "Bericht ü b e r eine V e r s u c h s r e i h e b e t r e f f e n d die Wirk u n g e n d e r Exstirpation d e r Schilddrüse," Arch, exper. Path. Pharmakol. 18 (1884), 25-34. 11. G e o r g e R M u r r a y , " N o t e o n the T r e a t m e n t of M y x o e d e m a by H y p o d e r m i c Injections of an Extract of the T h y r o i d Gland of a Sheep," Brit. Med. J. 1891, II, 796-797. 12. Louis R e h n , " U e b e r die Exstirpation des K r o p f s bei M o r b u s Basedow»;" Berlin klin. Wochenschr. 21 (1884), 163-166. 13. W. S. G r e e n f i e l d , "Some Diseases of the T h y r o i d G l a n d , " Brit. Med. J. 1893, II, 1261-1267. 14. A. von N o t t h a f f t , "Ein Fall arteficiellem a k u t e m t h y r e o g e n e m Morbus Basedow," Centralblatt inn. Med. 19 (1898), 353-379. 15. C. E. B r o w n - S e q u a r d , " E x p e r i e n c e d e m o n t r a n t la puissance d y n a m o g e n i q u e chez l ' h o m m e d ' u n liquide extrait d e testicules d ' a n i m a u x . " Arch, physiol. norm. path. [5] 1 (1889), 651-658; " N o u v e a u x faits relatifs a l'injection sous-cutane'e chez l ' h o m m e d ' u n liquide extrait d e testicules des m a m m i f e r e s , " Arch, physiol. norm. path. 2 (1890), 201-208. 16. C. E. Brown-Se'quard a n d A. d'Arsonval, "De l'injection des extraits liquides p r o v e n a n t des glandes et des tissus d e l'organisme c o m m e me'thode t h e r a p e u t i q u e , " Compt. rend. soc. biol. [9] 3 (1891), 248-250. 17. J . von M e r i n g a n d O . Minkowski, "Diabetes mellitus nach Pankreasexstirpation," Arch, exper. Path. Pharmakol. 26 (1890), 371-387. 18. B. Houssay, " T h e Discovery of Pancreatic Diabetes. T h e Role of Oscar Minkowski," Diabetes 1 (1958), 112-116. 19. E. H e d o n , "Sur la c o n s o m m a t i o n d u sucre chez le chien a p r e s l'extirpation d u pancreas," Arch, physiol. norm. path. [5] (1893), 154-163. 20. H . B a r c r o f t a n d J . F. Talbot, "Oliver a n d Schäfer's Discovery of the Cardiovascular Action of S u p r a r e n a l Extract," Postgrad. Med. J. 44 (1968), 6-8. 21. G. Oliver a n d E. A. S c h ä f e r , " O n t h e Physiological Action of Extract of the S u p r a r e n a l Capsules," Proc. Physiol. Soc. no. 1 (1894), I-IV. 22. G. Oliver a n d E. A. S c h ä f e r , " O n the Physiological Action of Extract of t h e S u p r a r e n a l Capsules," Proc. Physiol. Soc. no. 3 (1895), I X - X I I I . 23. G e o r g e Oliver a n d E. A. Schäfer, " T h e Physiological Effects of Extracts of t h e S u p r a r e n a l C a p s u l e s , " / Physiol. 18 (1895), 230-276. 24. Jokichi T a k a m i n e , " A d r e n a l i n e , the Active Principle of t h e S u p r a renal Glands a n d Its M o d e of P r e p a r a t i o n , " Am. J. Pharmacy 73 (1901), 523-531. 25. Τ . B. Aldrich, "A Preliminary R e p o r t on the Active Principle of t h e S u p r a r e n a l G l a n d , " Am. J. Physiol. 5 (1901), 457-461. 26. Friederich Stolz, " U e b e r A d r e n a l i n u n d Alkylaminoacetobrenzcatechin," Ber. 37 (1904), 4149-4154. 27. H . D. Dakin, " T h e Synthesis of Substances Related to A d r e n a l i n , " Proc. Roy. Soc. (London), Series B, 76 (1905), 491-497.

274

Notes to Pages 227-233

28. W. Μ. Bayliss a n d Ε. H . Starling, " T h e Mechanism of Pancreatic S e c r e t i o n , " / . Physiol. 28 (1902), 325-353. 29. E r n e s t H e n r y Starling, " T h e C r o o n i a n Lectures o n the Chemical Correlation of the Functions of t h e Body. Lecture I. T h e Chemical Control of the Functions of t h e Body." The Lancet 2 (1905), 339-341. 30. E. C. Kendall, " T h e Isolation in Crystalline F o r m of the C o m p o u n d C o n t a i n i n g l o d i n Which Occurs in the T h y r o i d , " J.A.M.A. 64 (1915), 2042-2043. 31. Charles R o b e r t H a r i n g t o n a n d G e o r g e B a r g e r , "Chemistry of T h y r o x i n e . I l l Constitution a n d Synthesis of T h y r o x i n e , " Biochem. J. 21 (1927), 169-181. 32. W. S. Swingle a n d J . J. P f i f f n e r , " A n A q u e o u s Extract of the S u p r a renal C o r t e x Which Maintains Life of Bilaterally A d r e n a l e c t o m i z e d Cats," Science 71 (1930), 321-322. 33. A. B u t e n a n d t , " U b e r die C h e m i e d e r S e x u a l h o r m o n e , " Ζ. angew. Chem. 4 5 (1932), 655-656. 34. Η. C l a u d e a n d Η. G o u g e r o t , "Sur l'insuffisance simultane'e de plusiers glandes ä secretion i n t e r n e (insuffisance p l u r i g l a n d u l ä r e ) , " Compt. rend, soc. biol. 63 (1907), 785-787. 35. H . E p p i n g e r , W. Falta, an^l C. R u d i n g e r , " U e b e r die Wechselwirk u n g e n d e r D r ü s e n mit i n n e r e r Sekretion," Zeit. klin. Med. 66 (1908), 152. 36. Harvey C u s h i n g , The Pituitary Body and Its Disorders. Philadelphia, Lippincott, 1912, p. 212-213.

20 Afterword 1. Oswald T . Avery, Colin M. McLeod, a n d Maclyn McCarty, "Chemical N a t u r e of t h e Substance I n d u c i n g T r a n s f o r m a t i o n of Pneumococcal T y p e s , " / . Exper. Med. 79 (1944), 137-158. 2. H. S t a u d i n g e r , " U b e r die Konstitution des Kautschuks. (6 Mitteilung)," ßer. 57 (1924), 1203-1208. 3. R o b e r t Olby, " T h e M a c r o m o l e c u l a r C o n c e p t a n d the Origin of Molecular B i o l o g y , " / . Chem. Educ. 147 (1970), 168-174. 4. Ε. C h a r g a f f , "Chemical Specificity of Nucleic Acids a n d Mechanism of T h e i r Enzymatic D e g r a d a t i o n , " Experientia 6 (1950), 201-209. 5. J . D. W a t s o n a n d F. H . C. Crick, "A S t r u c t u r e f o r Deoxyribonucleic Acid," Nature 171 (1953), 737-738; "Genetical Implications of t h e Struct u r e of Deoxyribonucleic Acid," Nature 171 (1953), 964-967. 6. E. C h a r g a f f , " P r e f a c e to a G r a m m a r of Biology," Science 172 (1971), 637-642. 7. J a m e s D. Watson, The Double Helix, New York, A t h e n e u m , 1969. 8. J a m e s D. Watson, Molecular Biology of the Gene, 2 n d ed. New York, W. A. B e n j a m i n , 1970. 9. G u n t h e r S. Stent, Molecular Genetics: an Introductory Narrative. San Francisco, W. H . F r e e m a n , 1971.

Index of Proper Names

Abernethy, J., 157 Adam of Bodenstein, 89 Adams, Ε. Q., 208 Addison, T „ 224, 226 Agrippa of Nettesheim, 88 Albertus Magnus, 66, 72, 73 Aldrich, Τ. B., 227 Alexander the Great, 25, 62 Alkmaion, 11, 16 Altmann, R., 187 Anaxagoras, 10 Anaximander, 7 Anaximenes, 7, 8, 15, 21, 26, 29, 36 Aquinas, Τ., 66, 72, 73, 74 Aristotle, 8, 18-25, 27, 30, 33, 39, 41, 55, 57, 59, 63, 65, 66, 70, 72, 73, 74, 77,81,84, 88,93,98 Arnald of Villanova, 77 Arrhenius, S., 208 d'Arsonval, Α., 226 Asclepiades of Bithynia, 32 Ascoli, Α., 187 Augustine, 63 Averroes, 65, 66 Avery, Ο. T „ 232 Avicenna, 56-61, 65, 66, 68, 72, 82

Bacon. Francis, 94 Bacon, Roger, 75 Barger, G„ 229 Barreswil, C., 164, 165, 168 Barthez, P. J „ 126, 149 Basso, S., 104 Baumann, C. Α., 205 Bawden, F. C., 188 Bayen, P., 130 Bayliss, W. M., 227 Beaumont, W„ 162-164 Beccari, I. B., 118, 119 Bernard, C., 151, 156, 164-170, 184, 224 Berthelot, M., 156, 180-182 Berthold, Α. Α., 224, 226 Berthollet, C. L., 141 Bertrand, G., 182 Berzelius, J . J., 143-145, 148, 149. 153-156, 161, 163, 165, 166, 172, 177 Bichat, X., 151 Bidder, F., 164, 165 Bishop, Κ. S., 220 Bjerrum, N., 209 Black, J „ 128-130, 132, 143 Blasius of Parma, 78

275

276

Index of Proper Names

Blondlot, Ν., 164 Boerhaave, Η., I l l , 114, 116-121, 122, 124, 141,142 Boethius, 39 Bopp, F., 174 Bordeu, T. de, 224, 226 Borelli, G. Α., 105-108, 119 Bouchardat, 166 Boussingault, J. B., 167-170, 191 Boyle, R„ 94, 107-109, 118 Bracannot, H., 174 Bredig, G., 208 Brooke, J. H„ 155 Browne, C. Α., 118 Brown-Sequard, C. E„ 224-226 Brücke, Ε., 152 Brunner, J. C. von, 103 Brunschwygk, H., 78 Buchner, E„ 182 Büchner, H„ 182 Budd, 212 Butenandt, Α., 229 Cagniard de Latour, C., 177 Caldwell, C„ 158 Capella, M., 39 Carminati, B„ 127 Cavendish, H„ 130, 131, 134 Celsus, 39 Chalcidius, 39 Chargaff, E., 232, 233 Chauliac, Guy de, 68 Chevreul, Μ. E„ 147, 161, 184 Chick, H., 219 Chittenden, R. H„ 184 Claude, H., 229 Cohn, Ε. J., 210 Cohn, F., 152 Colbatch, J., 103 Colombo, 61 Constantine, Emperor, 38 Constaminus Africanus, 64-66, 70 Copernicus, 79, 92 Cordus, V., 90 Cori, C., 204 Cori, G., 204 Cranston, J. Α., 129 Crawford, Α., 132, 134, 189 Crick, F. H. C., 232 Crispus, B., 40 Cullen, W„ 122

Curtius, T., 185 Cushing, H., 229 Dakin, H. D., 227 Dam, H„ 220 Davis, M., 217 Debus, Α., 88, 90, 91, 108 Democritus, 29, 30, 32 Descartes, R„ 93, 98-100, 104, 105 Diogenes of Apollonia, 15, 29, 30 Döbereiner, J. W., 155 Driesch, H„ 159 Drummond, J. C., 216, 217, 220 Du Bois-Reymond, E., 152 Duchesne, J., 89, 109, 118 Duclaux, E. P., 181 Dujardin, F., 152 Dumas, J. Β. Α., 154, 167-170 Duncan, D„ 99 Dunglison, R., 163 Eberli, J., 165 Eggleton, G. P., 204 Eggleton, P., 204 Ehrlich, P., 228 Eijkman, C„ 215, 216, 219 Embden, G. G., 203, 204 Emmett, Prof., 163 Empedocles, 8-10, 11, 12 Epicurus, 30 Eppinger, H., 229 Erasistratus, 26, 28-30, 33, 34, 35 Erastus, T „ 89 Euclid, 37 Euler, H. von, 220 Evans, Η. M„ 220 Faha, W., 229 al-Farabi, 57 Faraday, M., 196 Fehling, Η., 168 Fernel, J., 88, 89, 98, 111 Ficino, M., 69, 86 Finegold, H., 178 Fischer, E., 170, 175, 184-186, 208 Fischer, H., 195 Fiske, C. H„ 204 Fletcher, W. M., 203 Foligno, G. da, 69 Folin, O., 207 Fourcroy, A. F., 140-142, 145, 146, 163, 186

Index of Proper Names Frölich, Τ., 216 Funk, C„ 215-220 G a h n , J. G., 140 Galen, 11, 27, 32-36, 37, 39-42, 46, 55, 57-61, 64-70, 76-78, 81, 82, 88, 89 Galileo, 7 7 , 9 1 , 9 2 , 9 3 , 9 9 G a r r o d , Α. E„ 211 Gay Lussac, J. L., 146 G e r a r d of C r e m o n a , 65 G e r h a r d t , C., 155 Gilbertus Anglicus, 67 Glauber, J . R„ 101, 102 Glisson, F., 106, 124 Gmelin, L„ 162-164 G o d d a r d , J., 106 Goedel, F., 185 Goldberger, J., 219 Gougerot, H., 229 Graaf, R. de, 101, 102 Greenfield, W. S., 225 Grijns, G., 215 Grimaldi, F. M„ 118 Guerlac, H., 108, 140 Gull, W. W„ 225 Gundisallinus, D., 65 Hales, S., 121, 123, 128, 129 Hall, T., 113 Halle, J. N., 142 Η aller, A. von, 111, 121-126, 139, 142 Haly Abas, 55 H a m m a r s t e n , E., 188 H a r d e n , Α., 182, 203 H a r d y , W. Β., 209 H a r i n g t o n , C. R„ 229 Harvey, W „ 9 1 , 9 8 , 107 Hatchett, C., 141 Hawkins, J „ 103, 212 H a w o r t h , W. N „ 221 H e d o n , E„ 226 Helmholtz, H „ 152, 191 H e l m o n t , J . B. van, 79, 89, 91, 93-99, 100-102, 104, 107, 110, 112, 120, 121, 128, 160 H e n s e n , V., 170 Heraklitos, 7, 8, 13, 14, 31, 74 H e r m a n n , G., 201 Herodicus, 27 Herophilus, 26 Hess, Α., 218, 219

277

Hevesy, G., 208 H i g h m o r e , N., 104 Hildegard of Bingen, 70-72 Hippocrates, 11, 32, 64, 67 H o f f , E., 94 H o f f , J. H. van't, 184 H o f f m a n n , F., 112, 114-116 Hofmeister, F., 185 Holst, Α., 216 H o n o r i u s of A u t u n , 32 Hooke, R„ 88, 108 Hopkins, F. G., 202, 203, 214, 217, 223 Hoppe-Seyler, F., 186, 195, 197 Horsley, V., 225 H u n a i n ibn Ishaq, 54, 57, 64 H u n t e r , J „ 127 Huxley, T „ 152 Ibn Khaldun, 6 1 , 6 2 Ibn Nafis, 61 Ibn Sina. See Avicenna Ibn Wahshiya, 60 Ingen-Housz, J., 136 Isaac J u d a e u s , 64 Isadore of Seville, 39, 63 Jabir ibn Hayyan, 56 Jacobs, W. Α., 188 Jevons, F. R„ 119 J o h a n n e s Hispaniensis, 65 J o h n of Rupescissa, 77, 78 J o h n s o n , W. Α., 205 Jones, W. H. S„ 15 J o r g e n s o n , B. S., 150, 153, 156 Joule, J . P., 191 K a r r e r , P., 221 Keilin, D„ 198, 199 Kendall, E. C„ 229 Kendrew, J . C., 211 Kiliani, H „ 184 al-Kindi, 54 King, L. S„ 36 Kirchhoff, G. S„ 155, 166 Klickstein, H. S., 150 Knoop, F., 205, 206, 207 Kocher, T., 225 Ko H u n g , 47 Kolbe, H., 156 K o n r a d von Megenberg, 76 Kossei, Α., 187

278

Index of Proper Names

Krebs, Η., 205 Kühne, W„ 167, 181, 184 Küster, F. W„ 208 Küster, W„ 195 Kützing, F. T „ 177 Lagrange, J. L., 133 Lao Tzu, 44, 46 Laplace, P. S„ 133, 134 Laquer, F., 203 Lavoisier, A. L., 121, 131-136, 138, 141, 142, 143, 167, 189, 195 Le Bel, J. Α., 184 Leeuwenhoek, Α., 117 Lehmann, C. G„ 164 Lemery, N., 105 Leuchs, E. F., 166 Levene, Ρ. Α., 187, 188, 232 Levey, Μ., 54 Liebig, G., 194 Liebig,J„ 142, 145, 155, 158, 159, 165, 170-75, 177, 178, 180, 181, 184, 186, 191, 192, 194 Lind, J., 103 Lindeboom, G. Α., 121 Lipman, T. O., 150 Lipmann, F. Α., 205, 206 Loeb, J., 210 Lohmann, K., 204 London, E. S„ 188 Lower, R., 108 Lucretius, 30, 31 Ludwig, K. F. W„ 152 Lunin, Ν. I., 213, 214 Lynen, F., 206 Macbride, D., 135 Macleod, C. M„ 232 MacMunn, C. Α., 197, 199 Magendie, F., 146, 151, 161, 164, 165 Magnus, H. G., 190, 191 al-Ma'mun, 54 Mandel, J. Α., 187 al-Mansur, 53 Martius, C., 205, 206 Maximilian II, 192 Mayer, J. R„ 190 Mayow, J., 88, 108-110, 114, 128 McCarty, M., 232 McCollum, Ε. V., 217-219 McKie, D., 154

Mendel, L. B„ 214, 217 Mendelsohn, Ε., 150 Menon, 27 Mering, J. von, 226 Meyerhof, O., 203, 204 Mialhe, L„ 166 Michaelis, L., 183 Miescher, F., 186 Mikeska, L. Α., 188 Minkowski, O., 226 Mitscherlich, E., 177 Mohammed, 53, 58, 60 Mohl, H. von, 152 Mondeville, H. de, 67 Mori, Τ., 188 Morichini, D., 141 Mulder, G.J., 148, 172-175 Müller,J„ 151, 152, 155 Multhauf, R. P., 78 Murray, G., 225 Nemesius, 40 Nemorarius, J., 78 Neuberg, C„ 204 Neumann, Α., 187 Nicolaus of Cusa, 78, 79, 94 Northrop, J. H„ 183 Notthafft, A. von, 225 Olby, R., 232 Oliver, G., 226, 227 Osborne, Τ. Β., 214, 217 Pachter, Η. Μ., 88 Pagel, W., 82, 86, 96 Paracelsus, 36, 76, 80, 81-90, 92, 93, 95-97, 103, 104, 109, 110, 120 Parmenides, 6 Partington, J. R., 108, 118 Pasteur, L„ 177-181 Payen, Α., 166, 176, 181 Pekelharing, C. Α., 214 Pepys, W. H., 141 Persoz,J. F., 166, 176, 181 Perutz, M. F., 211 Peter of Abano, 67 Petrus Hispanus, 67 Pettenkoffer, M. von, 191-194 Peyer, J. C., 103 Pfiffner, J. J., 229 Pflüger, E„ 193, 194, 201

Index of Proper Names Philip, Master, 74 Piccard, J., 186 Pirie, N. W., 188 Plato, 16-20, 30, 33, 39, 46, 55, 63 Pliny, 40 P o g g e n d o r f , J. C., 191 Poseidonius, 30 Prevost, J. L., 154 Priestley, J., 130-132, 135, 143 Proust, J. L., 174 Prout, W., 147, 157, 161, 162, 164 Ptolemy, 37 Purkinje, J . E., 152 Quercetanus. See Duchesne R a y m u n d of Toledo, 65 R e a u m u r , Sieur de, 126 Regnault, V. H., 192 R e h n , L., 225 Reichstein, T „ 221 Reil, J . C., 139, 151 Reiset, J., 192 Reuchlin, J., 88 Rhazes, 66, 69 Richerand, Α., 143 Ritthausen, H., 174 Robison, J., 130 Robison, R„ 204 Roscoe, Μ. H., 219 Rouelle, Η. M„ 141 R u b n e r , M., 194 R u d i n g e r , C., 229 R u t h e r f o r d , D., 130 St. Martin, Α., 162 Sala, Α., 90, 138 al-Samarquandi, 55 Sanctorius, 29, 79, 91 Sandras, 166 Sanger, F., 210, 211 Saussure, Ν. T . d e , 136 Sauvages d e la Croix, F. B. de, 127 Schäfer: see Sharpey-Schäfer Scheele, C. W., 130, 140, 143 Schelling, F. W. Α., 151 Schiff, M., 225 Schleiden, M. J „ 152 Schmidt, C„ 164, 165 Schmidt, C. I. Α., 174 Schmidt, G., 148

279

Schoenheimer, R„ 207, 208 Schönbein, F., 196 Schwann, T., 152, 165, 177 Scopoli, 126 Seguin, Α., 134, 135 Semon, F., 225 Senator, H „ 193 Sendivogius, 108 Senebier, J., 136 Serenus, 40 Servetus, 61 Seyler, 195 Sharpey-Schäfer, Ε. Α., 226, 227 Sharrock, R., 94 Sigerist, H., 3 Silliman, B., 163 Sörensen, S. P. L„ 209, 210 Spallanzani, L„ 126, 134, 194 Stahl, G. E., 98, 1 1 0 , 1 1 1 - 1 1 4 , 115, 126, 137, 178 Stanley, W. M„ 188 Stare, F . J . , 205 Stark, W., 146 Starling, Ε. Η., 227 Staudinger, Η., 232 Steenbock, Η., 218, 220 Stensen, Ν., 101, 102 Stent, G. S., 233 Stepp, W., 214, 217 Stokes, G. G., 195 Stolz, F., 227 Subbarow, Y„ 204 S u m n e r , J . B„ 183 Svedberg, T . . 210 S w a m m e r d a m , J., 117 Swingle, W. S., 229 Sylvius, F., 101-103, 106. 109, 117 Szent-Györgyi, Α., 199, 205, 206, 221, 222 Takaki, K., 213 T a k a m i n e , J., 227 T a w a d d u d , 60, 61 Teich, M„ 145 Telesio, B., 89 T e m k i n , O., 151, 152, 159 Thaies, 7 T h e n a r d , L. J., 146 Thrasymachus, 27 T h u n b e r g , T . L„ 198, 199, 205 T i e d e m a n n , F., 162, 163, 164

280

Index of Proper Names

Tiselius, Α., 210 Traube, Μ., 180, 182, 194, 196 Trithemius, 81 Tsou Yen. 45 Tswett, M„ 210 Turquet de Mayerne, I., 90 Underwood, Ε. Α., I l l Valentin, G. G„ 166 Valentine, Basil, 90 Varro, 38 Vauquelin, N. L., 134, 141, 145, 186 Verworn, M„ 201 Vesalius, Α., 92 Vickery, Η. B., 174, 175 Vitruvius, 39 Vöit, C., 191-194

Waddell, J., 219 Wangensteen, Ο. H., 165 Warburg, O., 197 Watson, J. D., 232, 233 Wedel, J. W„ 111 Weinstock, Μ., 218 Wharton, Τ., 101 Wieland, Η., 198, 199 William of Conches, 65 William of Occam, 77 Willis, T., 103, 104, 108, 109 Wills tatter, R„ 183 Windaus, Α., 219 Wirdig, S., 98 Wöhler, F., 154-156, 158, 178 Wollaston, W. H„ 174 Woodall, J., 103 Young, W.J,, 182, 203

Subject Index

Acids, mineral, 77; organic, 140, 147, 164; see also u n d e r individual acids A c u p u n c t u r e , 49 Adenine, 187 Adenosine triphosphate, 204, 205 A d r e n a l cortex, 221, 229 Adrenal gland, 224, 225, 226, 227 Adrenaline: see e p i n e p h r i n e Aerobe, 179, 181 Air, 7 - 1 1 , 13, 15, 17, 21, 26, 34, 69, 87, 88, 102, 104, 107-110, 121, 123, 128; see also P n e u m a Air, fixed. See C a r b o n dioxide Albumin, 87, 142, 143, 163, 165, 172, 173, 175 Alchemy: Chinese, 47, 48; E u r o p e a n , 75, 77, 78, 83, 84, 90; Greek, 41, 48 Alcohol, 77, 78, 177, 178, 181 Alexandria, 12, 25, 32, 42 Alkahest, 97 Alkali diseases, 102, 103 A m i n o acids, 174, 185, 208-211 A m m o n i a , 141 A m m o n i u m cyanate, 154, 155 Amylases, 166, 176 Anaerobe, 179, 181 Analysis, chemical, 139-142, 146, 147, 163, 166, 170

A n d r o s t e r o n e , 229 Animal chemistry, 143, 144-148, 160 Animalization, 119, 142, 143, 145 Animals, constitution of, 65, 66, 167, 168,173 Animism, primitive, 2; of Stahl, 112, 114, 1 1 6 , 1 2 6 A n o n y m u s Londinensis, 27-29, 31 Antibodies, 228 Antimony, 90 Antioch, 42 Apeiron, 7 Arabian Nights, 60, 61 Arabs, 42, 43, 53 Archeus, 84, 85, 96, 97, 117 Architecture, 39 Arginine, 206 Arteries, 26, 28, 34, 72 Ascorbic acid. See Vitamin C Assimilation, 3 5 , 7 6 , 119, 124, 167, 168, 175 Astrology, 4, 69, 75, 77, 83, 86, 88, 96 Atomic theory, 9, 10, 30, 31, 55, 99 A T P . See Adenosine triphosphate Bacteriology. See Microbiology Baghdad, 42, 53, 54 Balance, nitrogen, 145, 191, 192

281

282

Subject Index

Benzoic acid, 206 Beri beri, 213, 215-217, 219 Beta oxidation, 207 Bile, 24,39, 76, 89, 102, 118, 125; black, 13, 59; yellow, 13, 58, 59 Biochemistry, definition, 1, 202, 231 Bioenergetics, 205 Biogens, 202 Bias, 96 Blood, 13, 22, 34, 59, 68, 98, 115, 123, 190; circulation of, 61, 91, 98; color of, 107, 108, 131, 144, 190, 195; Menstrual, 21, 52; sugar, 169 Bologna, University of, 66 Bones, 23, 141 Brain, function of, 3,17,23, 58, 106, 123 Breath concept, Chinese, 47 Brethren of Sincerity, 56, 57 Buddhism, 44 Buffers, 162 Byzantium, 38, 40, 42, 53 Caloric, 133, 189, 190 Calorimetry, 132-134, 189, 192-194 Canon of Medicine, Avicenna's, 57, 61, 82 Carbohydrates, 118,125,147, 148, 157, 168, 169, 171, 172, 184, 192, 193, 202, 203,204 Carbon, 132, 141, 142, 143 Carbon dioxide, 95, 129, 130, 132-136, 189, 190, 203 Carotene, 220, 221, 229 Casein, 172, 173 Catalysis, 156, 165-167, 177 Causes, Aristotelian, 19, 21, 57 Cell theory, 152 Chain of Being, 55, 56 Chaos, 85-88, 95 Chartres, School of, 63, 65 Chemistry, 93, 112, 121, 122, 127, 128132, 138, 139, 140, 150, 153, 202 China, 2, 3, 43, 44-50 Cholesterol, 219, 229 Christianity, 37 Chromatography, 210 Chyle, 59, 90, 97, 102-104, 107, 119, 120, 125, 129, 160 Chyme, 150, 160, 164 Citric acid, 205, 206

Coction, 15, 18, 21, 22, 34, 36, 59 Coenzyme, 182, 183, 203, 204, 220 Coenzyme A, 206 Colloids, 209 Combustion, 34,104,107-110,112,114, 130,133,134,155,171,181,189,190, 197 Commentaries, 40 Confucianism, 44 Cori ester, 204 Creatine phosphate, 204 Cretinism, 225 Cycles, concept of, 205, 206 Cystine, 174 Cytochrome, 197, 199 Cytosine, 187 7-Dehydrocholesterol, 219 Dehydrogenase, 198, 199 Deoxyribonucleic acid, 188, 232, 233 Deoxyribose, 188 Dextrin, 166 Diabetes, 226 Diastase, 156, 166, 176, 181 Diet, 4, 1 4 , 2 7 , 3 3 , 5 1 , 5 2 , 6 5 , 7 1 , 116, 145, 146, 175, 194, 213, 214-216 Digestion, 15, 17, 22, 26, 28, 33, 34, 51, 59, 68, 71, 76, 85, 88, 89, 96, 97, 102, 104,113,114,117,118,124,125,126, 129, 144, 160, 162, 164, 166, 167 Distillation, 41, 77, 78, 120, 139 DNA: see deoxyribonucleic acid Dogmatic School, 32 Drugs: see pharmacology Dynamic state, 207, 208 Earth, 8, 9, 11, 13, 17 Eclectic School, 32 Edessa, 42, 54 Effervesence, 69, 102, 103, 104, 106, 109, 117, 118, 127 Effluences, 10, 28, 29, 31, 224 Egypt, 3 Electron transfer, 198 Electrophoresis, 210 Elements: Chinese, 45, 48; Paracelsian, 84, 89, 104 Embden ester, 203 Embden-Meyerhof pathway, 205 Emotions, 39

Subject Index Empirical School, 32 E m u l s i n , 177 Encyclopedias, 38, 39, 56 E n e r g y , c o n s e r v a t i o n of, 190, 191, 194; e x p e n d i t u r e , 134, 135, 192 Enzymes, 167, 169, 1 7 6 - 1 8 3 , 196, 211 E p h e d r i n e , 49 E p i c u r i a n i s m , 10, 30, 33 Epilepsy, 12 E p i n e p h r i n e , 227 E q u a t i o n , chemical, 139 Ergosterol, 219 Erythrocytes, 117, 125 E t h e r , 30 E x p e r i m e n t a l m e t h o d , 29, 75, 122 Faculties, n a t u r a l , 35, 36, 58, 117 Fat, 23, 122, 125, 147, 157, 166, 167, 171, 172, 1 8 4 , 1 9 2 , 1 9 3 , 2 0 2 , 2 0 4 , 206, 207 Fatty acids, 147, 166, 2 0 6 F e r m e n t a t i o n , 104, 113, 119, 127, 1 7 7 181, 202, 204 F e r m e n t s : ot V a n H e l m o n t , 95, 97, 117; see also E n z y m e s Fertilization, 21 Fibers, 115, 116, 122, 124, 139, 151 Fibrin, 142, 143, 163, 172, 173 Fibroin, 172 Fire, 7 - 1 1 , 13, 14, 17 Flavocomplexes, 199 Flavor, 161 Flesh, 22, 23, 34 F l u o r i n e , 141 F r u c t o s e - 1 , 6 - d i p h o s p h a t e , 203, 205 F r u c t o s e - 6 - p h o s p h a t e , 204 F u m a r i c acid, 205 Gall stones, 140 Gases, 9 4 , 9 5 , 121, 129, 130 Gastric j u i c e ; acidity o f , 87, 96, 113, 118, 126, 127, 144, 1 6 0 - 1 6 5 ; enzymes o f , 165 Gelatin, 116, 119, 143, 145, 163, 1 7 2 174 G e n e , 232 G l a n d s : see u n d e r individual g l a n d s Glucose, 166, 168, 169, 184, 203, 205, 224 G I u c o s e - 1 - p h o s p h a t e , 204

283

G l u c o s e - 6 - p h o s p h a t e , 204 G l u t e n , 118, 119, 141, 142, 172, 173 Glycerol, 140, 147, 166 Glycine, 174, 185 Glycogen, 156, 169, 170, 204, 205; of muscle, 170 Gnostics, 37 Gonads, 229 Graves' disease, 225 Greece, 2, 3 G u a n i n e , 186, 187 H a n d b o o k s , 37, 38, 40 H a r d e n - Y o u n g ester, 203, 205 H a r m o n y , 11, 13, 15 H a r r a n , 42 H e a r t , f u n c t i o n of, 3, 4, 10, 17, 23, 26, 34, 39, 40, 48, 58, 61, 72, 74, 75, 76, 103, 106, 107 H e a t : bodily, 113, 117, 132, 133, 134, 171, 181, 1 8 9 , 1 9 0 , 194; i n n a t e , 7 , 1 4 , 15,18,21,26,33,34,36,40,88,96,97,117 Helix, d o u b l e , 232 H e m o g l o b i n , 195, 197, 211 H i p p o c r a t i c C o r p u s , 11-13, 15, 16, 18, 21,30,57 H i p p u r i c acid, 206, 207 Hormones, 223-230 Hsien, 46, 47 H u m o r a l t h e o r y , 11, 13, 26, 32, 34, 39, 55, 5 7 - 6 1 , 64, 68, 69, 75, 80, 90, 2 2 3 H u m o r s , I n d i a n , 51, 52 H y d r o c h o l o r i c acid, 1 6 1 - 1 6 5 H y d r o c y a n i c acid, 140 H y d r o g e n , 130, 141, 197, 198 H y p o g o n a d i s m , 50 H y p o t h y r o i d i s m , 14, 225 H y p o x a n t h i n e , 186, 187 I a t r o c h e m i s t r y , 81, 87, 8 9 - 9 1 , 93, 100, 101, 103, 111, 112, 125 Iatrophysics, 9 1 , 9 3 , 100, 105, 111, 113, 1 1 5 - 1 1 7 , 125 Iliaster, 84 I n d i a , 2, 3, 4 3 I n d o p h e n o l oxidase, 199 I n o g e n , 201 Insulin, 210 Intelligence, 14, 22 I r o n , 123, 144, 195, 197, 198

284

Subject Index

Irritability, 124 Isma'iliya, 56, 57 Isodynamic law, 194, 212 Isoelectric point, 209 Isomerism, 155 Isotopes, 207, 208 Jabirian Corpus, 56 J u n d i S h a p u r , 42, 52-54

Montpellier, University of, 66 Motion, 113, 115, 117 Muscle, 105, 106, 109, 117, 124, 143, 194,202-204 Museum of Alexandria, 25 Mutakallimun, 55 Mutations, 211 Myoglobin, 211 Myohaematin; see cytochrome Myxedema, 225

Kidney, 24, 48, 59, 107, 145, 154 Laccase, 182 Lactic acid, 140, 144, 161, 164, 165, 170, 178, 203, 204 Lacticidogen, 203 Lead tracers, 208 Lecithin, 186 Leeches, 7, 39 Leiden, University of, 101, 116 Leucine, 174 Liver, function of, 3, 4, 23, 34, 39, 48, 58, 59, 76, 154, 169, 170, 206, 224 Lungs, 23, 26, 3 4 , 4 8 , 6 1 , 107, 108, 113, 119, 120, 132-135, 189 Macrocosm-microcosm theory, 2, 4, 6, 8, 10, 16, 1 7 , 2 0 , 4 1 , 4 5 , 48, 50, 52, 70, 83, 88, 96 Macromolecules, 232 Malaria, 33 Malonic acid, 205 Marrow, 23 Medicine: Arabic, 56, 57, 59-62; Chinese, 4 7 - 4 9 ; Egyptian, 4; Greek, 7, 11-13, 15, 17, 27, 31, 32; Indian, 50; Medieval, 40, 64, 66, 67; Mesopotamian, 3; R o m a n , 39 Mercurial d r u g s , 87 Mesopotamia, 3 Metabolism, 193, 194; carbohydrate, 169, 1 7 0 , 2 0 2 - 2 0 6 ; fat, 206, 207; mineral, 194; protein, 207-211 Methodist School, 32 Microbiology, 178, 180, 212 Microcosm. See Macrocosm-microcosm theory Microscope, 115, 117, 124 Miletos, 5, 7 Milk, 22, 117, 119, 125, 175, 214 Minerals, 56

Naturalists, Chinese, 45, 46, 48 Naturphilosophie, 151 Neoplatonists, 37, 42, 56 Nerve, 100, 101, 104, 105, 106, 109, 123,223 Nerve juice, 106, 115, 117, 123, 124 Nestorians, 42, 5 2 - 5 4 N e u b e r g ester, 204 Nicotinic acid, 199, 216, 220 Nisibis, 42 Niter, 88, 104, 108, 109 Nitric oxide, 131 Nitrogen, 130, 132, 141-143, 145, 146, 191, 192 Nucleic acids, 186-188, 231-233 Nuclein, 186, 187 Nucleosides, 187 Nucleotides, 187 Nutrition, 9, 13, 14, 23, 29, 35, 142, 171, 173, 191 Ornithine, 206 Oxaloacetic acid, 205, 206 Oxidation, 133, 136, 191, 194, 195-198 Oxygen, 110, 112, 114, 130-136, 141, 171, 172, 181, 189, 190, 194-198 Oxyhemoglobin, 195 Ozone, 196 Pancratic juice, 101-103, 113, 118, 124, 166, 167, 168, 227 Pantothenic acid, 206 Paper, 54 Paris, University of, 66, 90 Pasteur effect, 179 Pectase, 182 Pellagra, 217, 219 Pepsin, 165, 177, 183, 184 Peptide b o n d , 185, 186

Subject Index Peptones, 185 p H , 209, 210 Pharmacology, 3, 32, 33, 49, 54, 55, 59, 65, 86, 90 Pharmacopoeias, 90 Phenylaceturic acid, 207 Philosophy: Arabic, 54, 55; Chinese, 44; Greek, 5 - 7 , 11, 12, 15, 38; Indian, 51 Phlegm, 13, 58, 59 Phlogiston, 110, 112, 114, 116, 131 Phosphate esters, 203, 204 Phosphoglyceric acid, 204 Phosphoric acid, 187 Phosphorus, 141, 175, 186 Photosynthesis, 135-137 Physiology, 89, 121, 122, 127, 150, 153 Pineal gland, 100 Pituitary gland, 229 Plague, 69, 86 Plants, 22, 23, 5 6 , 9 4 , 108, 114, 118, 121, 135, 136, 137, 143, 147, 156, 167, 168, 170, 172, 173, 208 P n e u m a , 7, 26, 30, 33, 34, 36; connate, 20,21 Pneumatic t r o u g h , 121 Pneumatist School, 32 Poisons, 60 Polypeptides, 185, 186, 208 Pores, 9, 10, 28, 2 9 , 3 1 , 3 2 Porphyrin ring, 195 Proteins, 116, 118, 119, 125, 147, 148, 157,167,170-175,183-187,192,193, 201, 202, 204, 207-211, 232, 233 Protoplasm, 152, 159, 202 Prout's hypothesis, 161 Provitamins, 220, 221 Psyche. See Soul Purines, 187, 232 Putrefaction, 119, 126, 127, 135 Pyridine nucleotides, 199 Pyridoxin, 220 Pyrimidines, 187, 232 Pyruvic acid, 204-206, 211 Pythagoreans, 10, 11, 16 Quadrivium, 39 Qualities, f o u r , 9, 18, 19, 30, 32, 55, 59, 6 4 , 6 5 , 6 7 , 7 6 , 80, 117 Quantification, 29, 32, 78, 79, 91, 93, 130,138 Quintessence, 20, 78

285

Ravenna, 40 Reduction, 195 Reproduction, 21, 52, 72, 73 Respiration, 7, 10, 15, 17, 107, 108, 110, 114, 123, 130-134, 1 8 9 , 1 9 2 , 1 9 4 , 2 0 4 Respiratory enzyme, 197, 199 Respiratory quotient, 193 Riboflavin, 219, 220 Ribonucleic acid, 188, 233 Ribose, 187 Rickets, 218 RNA. See Ribonucleic acid Robison ester, 204 Rome, 31, 37, 38 Salerno, School of, 63, 64, 66, 70 Saliva, 33, 101, 102, 113, 166 Salivary glands, 101 Sarcode, 152 Sarkin. See Hypoxanthine Scurvy, 103, 1 4 6 , 2 1 2 , 2 1 6 , 2 1 7 Secretin, 227, 228 Semen, 21, 22, 47, 51, 52, 59 Sensibility, 124 Signatures, 86, 87 Sodium chloride, 162 Solidism, 32 Solvent extraction, 139, 140 Soul, concept of: Aristotelian, 20, 56; Chinese, 47; Indian, 51; Medieval, 72-74; Platonic, 17, 20; PreSocratic, 8,20; Pythagorean, 16; Stahl, 112-114; Stoics, 30; Van H e l m o n t , 96 Soul, rational, 72-74, 98, 100 Specific dynamic action, 194 Specificity, 36, 70, 81, 85, 95, 98, 110, 120 Spleen, 23, 39, 48 Spirits: animal, 100, 103, 104, 115; rational, 59, 98; psychic, 59; vital, 26, 5 9 , 6 1 , 6 2 , 7 2 , 98, 104 Spiritus rector, 120 Starch, 118, 141, 155, 156, 166, 167 Stereochemistry, 184 Steroids, 50, 219, 229 Stoics, 28-30, 32 Stomach, 35, 59, 85, 88, 107, 119, 124, 161, 162 Succinic acid, 205 Sucrose, 168, 180

286

Subject Index

Tao, 44-46, 48 Taoism, 44, 46, 48 Tartar diseases, 85 Teeth, 141 Teleology, 16-19, 24, 30,31, 33, 35, 36, 46 Temperments, 32, 58, 60, 70 Testes, 22, 224 Thymine, 187 Thymus gland, 187 Thyroid gland, 225 Thyroxine, 229 Timaeus, 16, 17, 39, 63 Tobacco mosaic virus, 188 Tonicity, 113 Tracer technique, 207, 208 Translations, 42, 52, 54, 64, 65 Trivium, 39 Tyrosine, 174, 175 Trypsin, 167, 184 Ultracentrifuge, 210 Ultraviolet irradiation, 218 Universities, 63 Uracil, 187 Urea, 120, 141, 145, 154, 155, 206 Urease, 183 Uric acid, 140 Urine, 29, 50, 59, 87, 103, 107, 117, 120, 141

Vacuum, 26, 35 Veins, 28 Vitalism, 98, 111, 114, 125, 126, 143, 149-159, 202 Vitamin A, 49, 146, 212, 217, 218, 220, 221, 229 Vitamin B, 217, 218, 219 Vitamin C, 217, 221,222 Vitamin D, 218, 219, 220 Vitamin E, 220 Vitamin K, 220 Vitamins, 194, 212-222 Vulcan, 84 Water, 7,8,11, 13, 14, 17,94, 134, 136, 137, 141 Work, 171, 175, 190, 192 Xanthine, 186, 187 Xerophthalmia, 146, 218 X-ray diffraction, 211 Yang, 45, 47, 49 Yeast, 177-18U, i82, 186, 187, 203, 204 Yin, 45, 47-49 Zwitter ions, 208, 209 Zymase, 182