FUNCTIONS OF THE CEREBRAL HEMISPHERES 495 



the action of strychnine, or the toxin of tetanus. After administration 

 of either of these it is impossible to evoke inhibition of any muscle. 



FIG. 225. 



Anus & Vagina 



Toes 



Ankle--., 

 Knee 

 Hip ., " 



Shoulder 

 Elbow 

 Wrist ~* 



.- Sulcus . . 



' .centraliS 



Abdomen 



Fingers 

 & thumb 



C ' ' ' 



Ear- / 



Eyelid. .-'Closure / 



Nose f j* w Opening \ 



of jaw Vocal 



cords Mastication 



Sulcus centra/is 



FIG. 226. 

 Sulc.Centnil, Anus . * Vagina. 



Sulceotloso 



SvJLc.porif 



enu: many. 



Sulc. calcarin 



C.S S. del. 



FIG. 225, outer surface ; FIG. 226, inner surface of brain of chimpanzee, 

 showing movements obtained by excitation of the motor areas. 

 (SHERRINGTON.) 



Excitation of the cortical centre for the movements of the jaw causes 

 contraction of both closers and openers of the jaw, i.e. a strife in 

 which the stronger masseter muscles predominate, so that the jaw is 

 firmly closed. 



