The Excitable Cortex of the C'himpaii/ee, ()ran<;-Ut«n. and (Jorilla 1G3 



I'inna ol Har. — Movements rarely alone, almost always associated 

 with other movements of the face ; focal area lies partly buried in sulcus 

 post-centralis. The area seems larger in the chimpanzee than in the 

 o ran if. 



Cheek and Chin. — Movements were elicitable, but not common. 



Eyebrow and Frontalis. — Movement alwa^'s contralateral; tield in 

 upper part of facial area. 



Tongue. — Movements of tongue were obtainable from a very largr 

 area, in which they were usually the predominant ])rimary movements. 

 The}' were extremely varied in their form and se<juence, almo.st battling 

 verbal description. For the most })art they could be grouped under the 

 headings retraction, protrusion, rolling on long axis, upcurving of base or 

 tip, and hollowing of upper surface from side to side. 



Protrusion very rarely carried the tongue tip be^-ond the lips. The 

 appearance of the movements fre(iuently suggested that they were part 

 actions in mastication, licking, lapping, and swallowing. Thus one not 

 infrequent was a thrusting of the tongue against the inside of the cheek- 

 pouch as though to remove food thence ; again, a rhythmic movement of 

 licking or lapping; again, a heaping of the back of the dorsum against the 

 back of the palate, followed by contraction of the faucial opening as though 

 in swallowing. Occasionally the tongue was drawn back or thrust forward 

 straight; much more commonly the retraction or protrusion was deviated, 

 the deviation being sometimes to the ipsilateral, sometimes to the contra- 

 lateral side. Retraction and protrusion were evidently much commingled 

 in their I'epresentation in the cortex, but on the whole protrusion seemed 

 situated lower down the convolution than was retraction. Sometimes the 

 protrusion of tongue was accompanied by closing of jaw, and then 

 occasionally the tongue was nipped by the teeth, recalling the biting of 

 the tongue in epilepsy. On many occasions the points of excitable cortex 

 farthest down of all in the convolution evoked movement confined to 

 the tongue tip. 



Jaw. — Opening and closing were both elicitable, but the former has a 

 considerably larger field of points than has the latter; the latter's field 

 seems to lie the farther forward and not to extend nearly so far down, 

 at least as a primary movement, although in sequence to opening it extends 

 far downwards. Rhythmic chewing, a movement observed by Ferrier as 

 readily elicitable from the cortex of the cat, dog, and monkey, was observ- 

 able in the anthropoids, and was got from points low down and far forward 

 at the foot of the convolution. The jaw was not infrequently deviated 

 towards the contralateral side as well as opened or closed. By dividing 

 the symphysis it was found that the cortical representation is mainly uni- 

 lateral, although when the two lateral halves are normally conjoined by the 

 symphysis the unilateral representation in the hemisphere is mechanically 

 obscured. 



Hyoid. — Lifting of hyoid from a restricted part of lingual area. 



