The Excitable Cortex of the Chimpanzee, Orani^-rtaii, ami (Jorilla 203 



fissure across the precentralis as there usually is at that part, and the 

 jjreat veins over-runnintj the ijyrus there bein<; not so lari,fe as usual. The 

 individual movements ol' index and thumb were easily elicitable. A narrow 

 zone of representation of neck was demonstrable between hand and upper- 

 face rejjion at the t^enu inferius. The various movements elicited from 

 precentralis were in no case at all choreiform. "Epilepsy" was evoked by 

 atroni; and prolonijed stimuli, but it remained almost confined to the part 

 implicated in the primary movement beloui^ing to the focus excited, and 

 did not spread. 



The precentralis was then ablated for its whole length, except that a 

 narrow transverse .strip at its top end was left next to the longitudinal 

 sinus: and for its whole width, except that a strip 1-2 nnn. wide was left 

 along the posterior border next post-centralis, and that the arm annectant 

 to middle frontal gyrus and leg annectant to superior frontal gyrus were 

 not far trespassed upon. 



The wound was then closed aseptically. 



On recovering from the operative narcosis the animal was seen to be 

 hemiplegic in right face, arm, and leg. Next day, 2Sth, the face was 

 asymmetrically posed ; the cheek bagged on the right side ; the na.sal fold 

 was less marked right than left; the right half of the mouth was not fully 

 closed, whereas the left was. When the eyes closed the play of the upper 

 lids seemed bilaterally equal, but the play of the lower edges of the 

 palpebral fissures seemed greater and stronger for right than left eye. The 

 tongue lay in the mouth, with its mid-line, especially just behind the tip, 

 .slightly to left of the mid-line of the mouth. The play of the lips, both in 

 protrusion and in retraction, was very much greater on the left side than 

 the right; indeed, the right half of both lips seemed in flaccid paralysis. 

 Careful examination failed, however, to detect any difference in posture or 

 movement betw'een the forehead, eyebrows, or upper eyelids, right and left. 



Right hand and right foot were often moved fairly extensively, but 

 both were markedly paretic. It was several times noticed that flexion of 

 the right fingers and hand accompanied willed movements of the left arm, 

 and that folding of the right toes accompanied willed movements of the 

 left leg. Movements of right shoulder were poor and weak. On scratching 

 the sole of the right foot the digits were extended and spread, but scratch- 

 ing similarly the left sole induced no movement. Tickling the right side 

 of the face with a straw evoked lively action of the face ; similar tickling 

 of the left side of face evoked no facial action. 



The pupils were equal ; no disturbance of eyeball movements was 

 detected, though frequently looked for. 



July 29 (fig. 26). — Animal climbs about cage a little, but practically 

 makes no use of right arm, though some use of right leg, holding bars of 

 cage fairly well with right foot : is not feeding well. 



July 30. — Refuses food. Right hemisphere exposed under deep narcosis, 

 and then explored by faradisation and mapped. Results resemble those 



