NERVOUS SYSTEM. VERTEBRATA. 455 



the Simian sulcus is chiefly instrumental in accommodating 

 the expanding cortex in this region. This Cercopithecoid 

 arrangement affords a striking contrast to the condition 

 found in the Gorilla and in Man. There is a typical 

 calloso- marginal sulcus. 



The floccular lobe seems to conform to the usual human 

 pattern. It is composed of a plump oval mass of folia 

 which completely hides the flattened diminutive para- 

 flocculus. 0. C. 1338 i a ; 1338 I a *. 



D. 666. The brain of a Chimpanzee (Anthropopithecus troglo- 

 dytes), which has been subdivided by a mesial sagittal 

 section. The arteries have been injected. 



In this specimen the anterior insular area is depressed 

 and the limiting sulci almost meet. It is of interest to 

 note that the relations o branches of the middle cerebral 

 artery to this insula and its diminutive opercula are iden- 

 tical with those in the human brain. 



A short sulcus proceeding backward from the fronto- 

 orbital toward the superior limiting sulcns is of interest 

 as an indication of the expansion of the cortex in this 

 region, which leads to such marked results in the human 

 brain. 



There is a remarkably close agreement between the 

 features of these cerebral hemispheres and those of D. 664. 



The structures cut in the mesial sagittal section are 

 exceedingly clearly shown. They closely resemble the 

 corresponding human structures. 



The inferior transverse sulcus is present in a different 

 form in the two hemispheres. In the left hemisphere 

 there is a complete precentral sulcus. Further evidence 

 of the variability of the calcarine and parieto-occipital 

 sulci is afforded by this specimen, but the variations are 

 not new, parallel instances having been described in the 

 Gorilla and Orang (vide supra). 



D. 667. The brain of a Chimpanzee (Anthropopithecus troglo- 

 dytes). 



This somewhat imperfectly-preserved specimen 

 tained in the Museum because it exhibits a very intei 



