'"I 



d'itnif (V//x fit the Anf//nijx>i(f Ajw 



37 



cell; and in this connection it is <>t' some interest to know that the same morphological pecu- 

 liarity is to be observed in corresponding cells of the brains of several other mammals lower 

 down in tlio scale (vide Addendum). Furthermore, it is interesting to learn that the clustered 

 or nest-like arrangement of giant cells is a probable index of high development, because this 

 arrangement, although not altogether unrecognisable in the ape, is not nearly so well-exemplified 

 as in man. And here again we have a reproduction of a lower animal characteristic. 



In point of size, the human plan is followed, for, in the leg area, larger cells are found than 

 in the arm area; and those in the trunk area are smaller still. I have also noted the presence 

 of particularly small elements, which we might call borderland cells, all along the anterior 

 margin of the area, and were it not for their typical shape and their richness in chromophilic 

 granules I would have hesitated to include them in the Betz cell category. 



Taking next their distribution, it is found, in regard to the small giant cell area on the 

 mesial surface of the hemisphere, that man and ape agree perfectly; and in further support 

 of my previously expressed opinion, that the hinder or post-Rolandic portion of the paracentral 

 lobule is non-motor, I can now say that, in this chimpanzee's brain, nothing resembling a 

 giant cell was discovered behind an imaginary line, extended upwards and over the margin, 

 in continuation with the fissure of Rolando. 



Again, also, it is observed that that portion of the area lying above the level of the upper 

 genu holds an immense advantage in cell number over other regions, and I also notice that 

 on the convexity of the hemisphere the cells extend further forward on to the base of the 

 superior frontal convolution, and the area consequently attains an appreciably greater breadth 

 than it does in the human brain, in a corresponding situation. On arriving at the superior 

 genu a sudden fall in cell-representation occurs, but the barrenness at this level is not 

 nearly so pronounced as in the human brain, probably owing to the fact that the annectant 

 gyrus is only poorly developed. Immediately after passing the genu a second and more marked 

 reduction in numbers takes place, and down to the lower extremity of the area which we believe 

 to preside over arm movements, and on into the neck area, the cells continue to be scanty. 

 And, lastly, I have to mention that no cells, which can be called true "giant cells" in point 

 of size, are discoverable in the face area. 



To illustrate the foregoing, I will here insert a list showing the number of cells 

 counted in successive transverse sections taken at intervals of 3 mm., proceeding from the 

 m:irgin of the hemisphere downwards. 



1. Section 3 mm. distant from margin of hemisphere. 



Superior Genu. 



1 cm. above end of Rolando. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 

 12. 

 13. 

 14. 

 15. 



6 



9 



12 



15 



18 

 21 

 24 

 27 

 30 

 33 

 36 

 39 

 42 

 45 



51 cells. 



49 



60 



53 



53 



" 



28 



13 



12 



10 



15 



4 



5 

 3 

 



