132 ' Mammalia, 



CEEEBEAL CONVOLUTIONS OP THE ANTHEOPID^ 

 (MAN) AND SIMIAD^ (APES AND MONKEYS.)* 



(Based on M.Gratiolet's jT/(???joe;Ve stir lesplis Gcribraux de V Homme et des Primates.) 



Four structural peculiarities serve to distinguish the Brains of 

 Man and of the Apes from those of all other animals : these are 



1 . The rudimentary condition of the Olfactory lobes. 



2. A perfectly defined Fissure of Sylvius. 



3. A posterior lobe completely covering the Cerebellum. 



4. The presence of a posterior Cornu in the lateral ventricles. 



In the Brain of no other animal are these characters found to co- 

 exist simultaneously. 



The Lemurs are excluded from this group, because in them the 

 Olfactory lobes are large, the Cerebellum is not completely covered, 

 and there is no posterior Cornu in the lateral ventricles. 



Although these four characteristics are sufficient warrant for class- 

 ing an animal amongst the Apes, even if the external surface of its 

 Brain be absolutely devoid of Convolutions, still wherever Convolu- 

 tions do exist, they are always found to be parts of a definite ground- 

 plan or type, which pervades the whole series. 



Owing to its medium development, the Brain of Cercopithecus 

 Saba3us displays most clearly the outlines of this ground-plan, as no 

 obscurity arises either from obliteration of the component primary 

 Convolutions, or from the development of secondary ones. In fact the 

 surface of the Cerebral Hemispheres of the higher Apes and of Man 

 is only a complication of that seen in the Cercopitheci, whilst that 

 of the lower Apes is a simplification of it. 



* This paper was communicated by S. J. Sharker, Esq., B.A., Jesus College, 

 Oxford. 



