6^2 THE HIGHER ANTHROPOIDS 



over int(j the lateral surfaee without the sharp clemareation of the limiting 

 ridge whieh surrouiuls the eerebellar eonca\'ity in lower speeies. 



The fissures of this undersurfaee of the oceij^ital lobe are identical with 

 those of the human brain. The prominence attained by the tip oi the tem- 

 poral lobe is somewhat greater than that in the intermediate primates. It 

 approaches more nearly to that of man. The uncus also is more pronounced 

 both in its elevation and its demarcation. 



All things considered, the convolutional and lissural patterns of the 

 human and gorilla brain coincide so closely that were it not for the great 

 disparity in size between the organs of these two species, the hemispheres of 

 the one might be mistaken for those of the other. 



THE CEREBELLUM 



With regard to the cerebellum, equally striking advances have occurred. 

 The entire organ has gained particularly in the region of the lateral lobes, 

 where expansion has produced conspicuous alterations in certain features of 

 its configuration. The tentorial surface is broader and Hatter. The folial 

 extension from the vermis to the lateral lobe is more pronounced for the 

 reason that the superior vermis is less obviously delineated upon this surface. 

 Its tendency to convexity in the \ermal region has been largely lost due to 

 expansion of the occij)ital lobes with a corresponding expansion in the lateral 

 lobes of the cerebellum. Upon the tentorial surface in one place only is any 

 degree of the former prominence of the \crmis still retained; this is near its 

 cephalic extremity in close relation to the inferior collieuli of the midbrain. 

 Here the vermal portitjn of the cerebellum is considerably elevated and 

 produces a corresponding depression between the occipital lobes, the post- 

 splenial fossa. The tentorial surface is entirely overhung by the occipital 

 lobes of the hemisphere, and the occipital notch, which in many lower 

 forms is quite wide, is now much reduced in size. 



