Journal für Hirnforschung: Band 5, Heft 3 1962 [Reprint 2021 ed.] 9783112519820, 9783112519813

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JOURNAL FÜR HIRNFORSCHUNG I N T E R N A T I O N A L E S J O U R N A L FÜR N E U R O B I O L O G I E I N T E R N A T I O N A L J O U R N A L OF N E U R O B I O L O G Y J O U R N A L I N T E R N A T I O N A L E DE N E U R O B I O L O G I E BEGRÜNDET

VON C É C I L E

UND OSKAR

VOGT

Unter Mitwirkung des Instituts f ü r Hirnforschung und allgemeine Biologie in Neustadt/Schwarzwald und der Arbeitsgemeinschaft f ü r vergleichende Neuroanatomie der Fédération mondiale de Neurologie (World Fédération of Neurology) HERAUSGEBER II. A

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Fig. 5. In layer A of the atrophic sector shown in Fig. 4 are a fasciculus of thicker degenerating fibres of passage in the centre of the picture, the fine undirected ,cortico-geniculate' fibres and a few thick normal fibres.

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Fig. 6. Layer 3 of the atrophic region of the geniculate nucleus in M/VCL/7, with both normal and degenerating fibres.

Bd. 5, Heft 3

A NAUTA AND GALLOCYANIN S T U D Y

1962

227

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m Fig. 7. T h e magnocellatur layer 2 in the same section from M/VCL/7 and near the site of Fig. 6 with the fragments of a degenerating fibre arrowed.

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Fig. 8. I n the stratum intermedium of the ipsilateral superior colliculus of M/VCL/7 are the nerve cells, undirected degenerating fibres running in their vicinity, degenerating fibres entering in the fasciculi and a normal fibre. V o g t , H i r n f o r s c h u n g , B d . 5, H e f t 3

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m Fig. 9. The same area of the contralateral superior colliculus on the N a u t a section used for Fig. 8 shows the cells, and a fibre bundle cut in cross section one fibre of which has a ring form. No degenerating axones are to be seen.

Fig. 10. The ipsilateral superior colliculus of cat C/VCL/13 in frontal section with fine degenerating fibres in the strata zonale and superficiale and a denser undirected degeneration, including some thicker fibres, in the stratum intermedium. The cortical projection does not enter in fasciculi, but laterally from the brachium.

Aus

dem

Max-Planck-Institut für Hirnforschung, Neuroanatomische F r a n k f u r t (Main), Germany

Abteilung,

(Prof. Dr. R. H a s s l e r ) and Department of Neurosurgery, University of Mississippi, Medical Center, Jackson, Mississippi, U. S. A. (Prof. Dr. O. J. A n d y )

The Septum (A Comparative Study on its Size in Insectivores and Primates) by H e i n z S t e p h a n 1 ) and O r l a n d o J. A n d y 2 )

Ten Figures

Introduction With reference to the septum, E l l i o t S m i t h (1895) stated, „. . . the commissure bed is diminishing in extend with the lessening importance of the olfactory sense." According to K a p p e r s et al ('36), the septum was considered as a basal center for the correlation of olfactory and visceral impulses and as an important way station from hippocampal to diencephalic structures. The question arises as to what anatomic and physiologic relationships actually exist between the septum and the olfactory, diencephalic, hippocampal and other brain structures. A comparative anatomic study was undertaken to answer the question. Quantitative developmental changes were determined for various brain structures among placental mammals which represented different points in the ascending scale of phylogenetic development. The twenty-one animals utilized extended from the lowest insectivores, through the lower primates. Insectivores and lower primates were chosen because, among living animals, they come closest to the evolutionary line leading to higher primates and finally to man. Fortunately, primates are well represented along different degrees of evolutionary development. Since body weights of insectivores are rather small, it was thought best to restrict this study to primates which have body weights in the same range. This allows for more direct comparison and thus for more significant findings. After having established this firm base line of comparison, studies in higher primates including man will be undertaken. x

) Supported in p a r t by Deutsche Forschungsgemeinschaft. ) Supported in p a r t b y U. S. P. H. Grant (B-815).

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230

H E I N Z S T E P H A N AND ORLANDO JJ . A N D Y

...

J° u , mal .

fur Hirnforschung

Method This study is based on a comparison of the volumes of various brain structures. The sizes of the brain and its components are influenced by several factors ( S n e l l , 1892; D u b o i s , 1897). One of the known factors which is the most constant and easily evaluated is body size (weight). If the influence of body size upon the various brain structures is known, it is possible to evaluate the influence of other factors such as degree of evolution, regression and specialization. 2

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Figure 1. Septum volumes plotted against body weight. Regression line in this and other figures, unless otherwise stated, were constructed from insectivores identified by encircled crosses = terrestrial Soricidae (Sm, Sa, Cr, Co) and Erinaceidae (Er.). Figurines: Crosses — (Se and Te), most primitive insectivores, (Ta) burrows with large hands; Star — (Ct), primitive and highly specialized, burrows with head and has small hands; Cross and wavy line — (Ne, Gm and Po), semiaquatic; Half animal figures — prosimians, low primates, (Gg) can see, hear and smell well and is agile, (Lo and Pe) are slow and lazy: Whole animal figures — higher developed primates, (Ao) nocturnal, all other primates (here Ca and Le) are diurnal; Combined half animal figure and cross — (Tu) may be classified as either a primate or insectivore.

The relationship between body size and volume of the brain and its parts is linear in a double logarithmic scale. This relationship has been investigated in some lower forms of insectivores, which can serve as basic forms for phylogenetic studies ( S t e p h a n '60 and '61). Soricidae and Erinaceidae were used because they represent insectivores in the same stage of evolution with different body weights. A regression line was constructed for these animals (fig. 1 and 2). Tenrecidae have been excluded because they are more primitive and we had no representative in the lower weight ranges.

B d . 5, Heft 3 1962

THE SEPTUM

231

Analyses were made by determining the correlation and regression coefficients. In order to visualize developmental differences of various brain divisions, their volumes were plotted on a percentage scale in which the basic forms were considered 100% (fig. 3).

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Figure 2. Neocortex volumes plotted against body weight. For figurine designations refer to figure 1.

Materials and Technique Animals Thirty-six brains representing twenty-one species of placental mammals were utilized for this study. Average brain and body weights were obtained from several animals in each species as previously listed by S t e p h a n ( ' 6 1 ) . Insectivores of fourteen different species represented seven of the existing eight families as follows: family Tenrecidae, Setifer setosus and Tenrec ecaudatus ; family Potamogalidae, Potamogale velox ; family Erinaceidae, Erinaceus europaeus ; family Soricidae, Crocidura russula, Crocidura occidentalis, Sorex

HEINZ STEPHAN AND ORLANDO J . ANDY

232

Journal fiir Hirnforschung

minutus, Sorex araneus, and Neomys fodiens ; family Talpidae, Talpa europaea and Galemys pyrenaicus; family Chrysochloridae, Chlorotalpa stuhlmanni; family Macroscelididae, Elephantulus fuscipes and Rhynchocyon stuhlmanni. Tupaia glis, in the classification of mammals, is located between the insectivores and primates. There is no unanimity of opinion as to which of these two orders it should be assigned. Primates are represented by three prosimians, Perodicticus potto, Loris gracilis and Galago demidovii which all belong to the family Lorisidae. Three anthropoid apes are represented by Callithrix jacchus and Leontocebus oedipus which belong to the family Callithricidae and Aotes trivirgatus, a primitive Cebidae. Histology

and

Photography

All brains were prepared with a perfusion of Bouin's solution immediately after being sacrificed. They were imbedded in paraffin, serially sectioned at 10 or 20 fx thickness and stained with cresyl violet. Two hundred and fifty sections were stained from each brain. Thus in the smallest brain, Sorex minutus, every section was stained and in the largest brain, Aotes trivirgatus, every 10th was stained. Fifty to sixty microscopic sections which were serially distributed at equal intervals in each brain, were directly projected on extra hard photographic paper 18 X 24 cm and photographed with a magnification of 9 to 35 times. Delineation

and volumetric determination

of brain

structures

Borders between the structures were determined by microscopic and photohistologic differentiation. They were outlined on the enlarged histological photographs and the components of each division were cut out and weighed. The paper was previously weighed in order to determine the number of square mm per gram. Distances between the histologic sections were calculated and thus volumes for each division were derived. For several brains, the volumes were compared and checked by planimetric measurements and were found to be very similar. Abbreviations Ao Ca Co Cr Ct El Er

Aotes trivirgatus Callithrix jacchus Crocidura occidentalis Crocidura russula Chlorotalpa stuhlmanni Elephantulus fuscipes Erinaceus europaeus Gg Galago demidovii Gm Galemys pyrenaicus Le Leontocebus oedipus Lo Loris gracilis

Ne Pe Po Rh Sa Se Sm Ta Te Tu

Neomys fodiens Perodicticus potto Potamogale velox Rhynchocyon stuhlmanni Sorex araneus Setifer setosus Sorex minutus Talpa europaea Tenrec ecaudatus Tupaia glis

Bd. 5, Heft 3 1962

THE SEPTUM

233

Results Septum compared with body weight Definitions: Septum included Diagonal band of B r o c a ( A n d y and S t e p h a n , '59). Body weight according to S t e p h a n ('61). The size of the septum in higher developed insectivores and in the primates is generally larger than in the lower insectivores (fig. 1 and 3). This is an unexpected finding in view of the commonly expressed thought, „the septum undergoes regression in higher developed forms such as primates and man". The septum does appear small in higher forms (fig. 4), but this is only relative (table), due to the exceedingly large development of other brain structures such as the neocortex. Table: The size of the septum in various insectivores and primates in relation to the whole brain (net tissue values). whole brain (mm3) 1 Aotes trivirgatus 2 Leontocebus oedipus 3 Callithrix jacchus 4 Galago demidovii 5 Loris gracilis 6 Perodicticus potto

r H till LIirupUlLL apes 0 Ti

• prosimians

Galemys pyrenaicus Elephantulus fuscipes Rhynchocyon stuhlmanni Potamogale velox Chlorotalpa stuhlmanni Talpa europaea Neomys fodiens Crocidura occidentalis Sorex araneus Erinaceus europaeus Crocidura russula Sorex minutus Setifer setosus Tenrec ecaudatus

%

14 753,4 8895,4 7467,2

89,6 63,6 51,2

0,61 0,71 0,69

3203,5 650 6,1 13212,2

25,8 42,6 114,0

0,80 0,65 0,86

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1,08

1 230,5 1 228,1 5680,2 3751,8 688,8 953,2 299,1 408,0 187,7 3027,9 168,5 103,3 1338,9 2508,2

20,2 16,7 81,5 49,8 11,3 15,0 6,4 6,9 3,9 50,4 3,5 2,0 24,8 40,8

1,64 1,36 1,44 1,33 1,64 1,58 2,15 1,70 2,08 1,67 2,05 1,96 1,85 1,63

7 Tupaia glis 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Septum (mm3)

• insectivores

Septum compared with neocortex and

hippocampus

Definitions: Neocortex included cingulate and retrosplenial regions and the Island of Reil. Hippocampus included the subiculum and fascia dentata according to R o s e ('27).

HEINZ STEPHAN AND ORLANDO J. ANDY

234

Journal fur Hirnforschung

T h e scale of the neocortex (fig. 3) shows that the three highest evolved primates had over 2 , 0 0 0 % increased neocortical development in contrast to the lower primates which were between 900 and 1 , 5 0 0 % , and the highest insectivores which were below 4 0 0 % . T h e scale was established in relation to the basic forms (fig. 2). Setifer setosus and Tenrec ecaudatus which were the most primitive insectivores, possessed the least amount of neocortex, lesser than the basic forms. Septum

Neocortex

Hippocampus El.

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Figure 3. The average volumes in the Soricidae and Erinaceidae were utilized to establish the 100% line. This line corresponds to the base line in figs. 1 and 2. The differences of the volumes of the septum, neocortex and hippocampus from those of base line forms of equal body size are expressed in percentages for each animal, according to the distances from the base lines in figs. 1 and 2. The short vertical lines on either side of the neocortex scale represent reduction of the magnified septum and hippocampus scales to correspond with that of the neocortex for comparison.

THE SEPTUM

B d . 5, Heft 3 1962

235

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Figure 4. Upper figure: Tenrec 1005, slide 966; lower figure: Aotes 387, slide 860. C-Commissura anterior; H-Hippocampus praecommissuralis; N-Neocortex; R-Rhinencephalon; S-Septum ; St-Striatum. Note that upper figure was more enlarged to facilitate comparison of size relationships.

HEINZ STEPHAN AND ORLANDO J. ANDY

236

Journal fur Hirnforschung

2

0.5

25

IS log

35 Neocortex

Figure 5. Septum volumes plotted against neocortex volumes. Dotted regression line obtained from insectivores with encircled crosses and solid line from all animals combined. For figurine designations refer to figure 1.

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Figure 6. Septum volumes plotted against hippocampus volumes. For figurine designations refer to figure 1.

Bd. 5, Heft 3

THE SEPTUM

1962

237

The maximum development of the septum (252% in Leontocebus) and of the hippocampus (354% in Elephantulus) is rather small in comparison with the neocortex. The difference in the increase between septum and neocortex is also expressed through the relativ flat rise of the regression line (a = 0,536 in fig. 5). The correlation between these two structures is poor. Especially the primitive Tenrecidae (Setifer and Tenrec) have a comparatively large septum in relation to the neocortex, in contrast to the primates. The correlation between septum and hippocampus (fig. 6) is much better. Only in Elephantulus and Rhynchocyon the hippocampus underwent relatively greater development than the septum (fig. 3 and 6). These animals are from a highly specialized insectivore family, Macroscelididae, and possesses a large and mobile snout and in contrast to all other insectivores, large eyes. Tenrec and Setifer represent the lowest insectivore family, Tenrecidae. They had a somewhat greater development of the septum than hippocampus. The ascent (