Dynamic Theory. 

 most destitute of convolutions. The little midas, or marmoset platyr- 

 rhine, has only one fissure on the outside, No. 5, the sylvian, although 

 it possesses both the hippocampal and posthippocampal (4 and 4') on 



Fia. 318. Top view of Brain of Dolphin. 



the septal, or mesial surface, these being the fissures over which are 

 folded the hippocampus major and hippocampus minor, respectively. 

 In the callithrix, another platyrrhine (fig. 330), several additional fis- 

 sures are to be observed, and it is to be noted that these are of the lon- 



/4 



FIG. 319. FIG. 320. FIG. 321. 



FIG. 319. Top of Brain of Tragulus, or Chevrotain, the smallest of Antelopes. 

 FIG. 320 Top of right half of cerebrum of Stag. 

 FIG. 321. Same of Giraffe. ( Hoofed mammals.) 



gitudinal sort, like the carnivores. In the macacus (fig. 330), another 

 platyrrhine, and the chimpanzee, a catarrhine ape, the fissures take on 

 the transverse position substantially, as in man. 



The division of the brain into three lobes appears the most natural, 

 making fissures 12 and 13 the boundaries ; but some anatomists count 



