Chap. XII.l 



BRAIN OP MAMMALS. 



427 



There early ap- 

 pears a fissure at 

 the side of the 

 cerebral hemi- 

 spheres, the sylvian 

 fissure (Figs. 182; 

 sy; and 184 (u) ; s), 

 which separates the 

 frontal from the oc- 

 cipital lobe ; this, 

 which is very shal- 

 low in the rabbit or 

 the musk-deer (Fig. 

 184; s), is deeper 

 in the pig or the 

 dog, and in man 

 divides into an an- 

 terior and a pos- 

 terior groove, be- 

 tween which is 

 placed the island 

 of Beil. The sur- 

 face of the hemi- 

 spheres is next 



8, Pi 



Fig. 184. Brain of Musk-Deer. A, from the side ; B, from above. 



(sure of Sylvius ; ss, superior external gyrus ; m, middle ; ii, inferior external 

 1S75 US ' 1 ^ lppocam l )al sy rus : o, supraort-ital gyrus. (.After Flower, P.Z.S., 



