X 



THE FOEE-BKAIN 



553 



12, observed movements of deglutition and partial or total con- 

 striction of the glottis and larynx associated with contraction of 

 the muscles of the neck, of the superior constrictors of the pharynx, 

 levatores veli-palatini, glosso-palatini, and tongue in a word, the 

 muscles which come into play in deglutition and phonation. 



The internal interhemispherical surface of the brain, while less 

 known (perhaps because more difficult to explore), also contains 

 excitable areas, although these have not been localised and defined 

 with sufficient accuracy. Lo Monaco found that the fore-part of 



FIG. 280. Plan of left hemisphere Macacus. Internal surface. (Horsley and Schiifer.) 



the marginal convolution contains the continuation of the sensory 

 motor zone of the external surface. 



Terrier first applied the method of faradisation to determining 

 the excitable area in the lower apes {Macacus cynomolgus). He 

 found that it extended over a larger surface than in the dog ; in 

 addition to the two central or Eolandic convolutions it comprises 

 the angular gyms, a portion of the upper tempero-sphenoid con- 

 volution, and part of the first and second frontal convolutions. 

 As shown by -Figs. 2*77 and 278, a larger number of centres for 

 given movements of different muscular groups can be identified in 

 this species of ape. 



For descriptive purposes, Beevor and Horsley (1887-88) 

 divided the excitable zones of the cerebral cortex of Macacus into 



