ANATOMICAL STRUCTURE OF ANTHROPOID APES. 195 



and Negro races the covering appears to be generally 

 imperfect. 



While the ground form of the gorilla brain 

 approximates to a long oval, and in this respect 

 resembles the human brain, the brain of chim- 

 panzees and orangs is of a round-oval form. This 

 is especially the case with the chimpanzee (Fig. 57). 

 In my opinion, the gorilla brain is distinguished 

 from that of the chimpanzee, but not from that 

 of the orang, by its very complex convolutions 

 (Fig. 56). 



In the gorilla, chimpanzee, and orang, the island 

 of Reil in the fissure of Sylvius is generally — at least, 

 according to my experience — overlapped by the 

 operculum, although there are instances in which 

 this is not the case. In these three anthropoids, as 

 Bastian justly observes, the fissure of Sylvius is 

 much less horizontal than in man, and occupies a 

 position more like that which it takes in the black 

 sea-cat monkey, the wanderers, and other macacas. 

 In the gorilla its direction is more horizontal than 

 in the two other species of anthropoids. The central 

 fissure, termed fissure of Rolando, is very marked, 

 especially in the chimpanzee (Fig. 57 E) ; but it 

 may also be easily traced in other species of anthro- 

 poids (Fig. 58, II., 56, R). The so-called simian 

 fissure between the parietal and occipital lobes of 

 the cerebrum (Meynart's elongated external occi- 

 pital fissure), presented in Fig. 58 s c, is very marked 

 in the chimpanzee (Fig. 57, d). The frontal lobes 

 of the gorilla brain are high, while those of the 

 chimpanzee are short and low. It is said that those 



