Comparative Anatomy of the Brain. 595 



five in man, some of them more or less artificial. A part sometimes 

 called the central lobe is the Island of Reil, situated inside of the fis- 

 sure of sylvius. It is the organ of speech. In the Dog, the part an- 



FlG. 322. FIG. 323. 



FIG. 322. Top view of Brain of the Rock Coney; Hyrax. 

 FIG. 323. Top view of right hemisphere of Horse. 

 FIG. 324.- Same of Rhinoceros. (Hoofed.) 



FIG. 324. 



swering to the Island of Reil is quite smooth, and the fissure of sylvius 

 is short, not extending over half way to the median or interhemispher- 

 ical fissure. The Island is, however, convoluted in the Porpoise and 

 in the Apes as well as in Man. 



Fia. 325. 



FIG. 326. 



Fia 328. 



FIG. 325. Top ofriaht hemisphere of Pig ( Sus). 

 FIG. 32G. Same of Lama (Auchenia). 

 FIG. 327. -Right *!!< lint in of Rock Cony (Hyrax). 

 Fia. 328. Same of Giraffe. 



The human brain in its development passes through stages similar to 

 conditions which are permanent in the quadrumana, as regards the con- 

 volutions. ( Owen. ) In the brain of a foetus of three months, the fis- 

 sures 4, 7, 2, 5, 13', 9 and 12 are already indicated, or more or less 

 developed, and it may be compared with the brain of the cebus. At 

 seven months the human foetus presents a striking agreement in the de- 



