PROSENCEPHALON OF MAMMALS. 



123 



104 



105 



sphere; notso longitudinally extended along the mesial margin of the 



hemisphere as in llyrax and Equus. 



The folds, / and m, figs. 102 -105, come 



into contact at the middle part of the 



interhemispheral fissure, and show 



their character as medial ones, in the 



larger Artiodactyles. In Cervus, fig. 



102, / and g blend anteriorly, and are 



continued into the frontal tract, n, 



the anterior longitudinal subdivisions 



of which are marked off by the short 



fissures, iV and u". In the Giraffe, 



fig. 103, the primary fissure, 10, is 



continued by a bend which may indicate 12, into the midfrontal 



fissure, 14"; in most Ruminants the supersylvian fissure, 8, extends 



into 14''. On the inner surface the same course of complexity adds 



106 107 



3 



Sus. 



Aucheuia. 



Hyrax. 



Giraff*. 



to the primary hippocampal, 4, callosal, 7, and entolambdoidal, 13', 

 fissures, shown by Tragulus and Ilyrax, the marginal, 6, super- 

 callosal, 7', and falcial, 15 ; the supercallosal, which is interrupted 

 in the Sheep and Ox, is 108 



continuous in the Giraffe. 

 Less significant secondary 

 fissures impress both fore 

 and hind parts of this sur- 

 face. Below the sylvian 

 fissure, 5, and fold, e, e', 

 a narrow undulated <sub- 

 sylvian ' fold, /', fig. 107, 

 Giraffe, divides them from 

 the ectorhinal fissure, 2 : it 

 is not present, at least as a 

 convolute tract, in Perisso- 

 dactyles : it is well marked and rises high up the sylvian fissure 

 in Proboscidians, fig. 108, f. We shall meet with this sub- or ento- 

 sylvian tract again : it attains its greatest extent of surface in Man. 



Elephant ; side view of cerebral hemisphere. 



