306 THE BRAIN OF QUADRUMANA. 



and in consequence of this, as well as of the smaller 

 relative development of the parietal lobes, the Sylvian 

 fissure deviates much more from the horizonal position 

 in the Orang than in either the Gorilla or the Chim- 

 panzee.* The lower and posterior border of the Cerebral 

 Hemispheres is notably more oblique than it is in Man, 

 owing principally to the small size and shallowness of the 

 occipital lobes. In this latter respect, as well as in the 

 generally deficient depth of the Hemispheres as compared 

 with those of Man, the Chimpanzee and the Orang are 

 closely allied. 



On the whole, it would appear that the convolutions of 

 the Gorilla's brain are slightly more subdivided and com- 

 plex than those of the Chimpanzee ; though in this respect 

 the brain of the Orang is, to about the same extent, 

 superior to that of the Gorilla. As regards the want of 

 exact symmetry of many of the corresponding convolutions 

 of the two Cerebral Hemispheres, that of the Orang also 

 approaches most closely to the still more marked asym- 

 metrical condition of the brain of Man. 



* This direction is very well seen in the figure given by Prof. 

 Bolleston (loc. cit., pi. 3, fig. 1), though it is not so distinct in that 

 of Gratiolet (see fig. 121 in text). 



