The Excitable Cortex of the Chimpanzee, Orang-Utan, and Gorilla 187 



in it of a number of points with thu movements they yielded was carefully 

 mapped. This record is reproduced in fig. 5, A. Focal epilepsy was very 

 readily provoked; it did not, however, spread; e.g. on several occasions 

 when an index finger point was excited the " epilepsy " remained confined 

 to index finger. Although faradisation of post-centralis did not provoke 

 any movement, it did, when the narcosis was light, seem each time to arouse 

 the animal. 



The part indicated by the enclosure within the dotted line on the map 

 (fig. 5, A) was then extirpated : care was taken to include the whole anterior 

 wall of tliL' sulcus centralis, i.e. down to the bottom of the sulcus. The wound 

 was then aseptically closed and surgical dressing applied. On the animal's 

 recovery f I'om the narcosis it was noted that right wrist Avas " dropped " 

 and that the thumb seemed quite paralysed, but that a little flexion and 

 extension of the three outer finj^ers occurred from time to time. The 

 shoulder seemed slightly affected, but the elbow not at all. No trace of 

 paresis of face or leg. The following morning the animal was found active, 

 feeding well, and in good spirits. There was no trace of facial or leg 

 paresis. Flexion or extension of the three ulnar fingers of right hand 

 occurred, but seemingly only when the hand was placed in contact with 

 some object, e.g. bars of cage. Movement of the thumb was seen only 

 under circumstances w^hen it might be passive ; indubitable active motion 

 of it was not seen. Movement of index fingrer was never seen. The hand 

 hung helplessly prone, and dropped at the wrist joint. Power to elevate 

 the shoulder seemed defective. No paresis noted at elbow. The defect at 

 shoulder probably seemed greater than it really was, for in the afternoon 

 on the cage door being set open, the animal ran out, and in climbing up the 

 outside of the cage it was seen to raise and protract the right arm well at 

 the shoulder. The grasp by the three ulnar fingers appeared to improve 

 during the day. In regard to the sensations of the right hand, clear 

 evidence was obtained that bending back either the thumb or little finger 

 was felt, and was unpleasing to the animal. 



Eight days after the operation. Small pieces of fruit, e.g. bits of a 

 grape, were fairly accurately picked up by the right hand. There seemed 

 a liability to misplace the whole hand. Fifteen days after the operation 

 great improvement had occurred in the use of the limb ; a cursory examina- 

 tion would hardly detect any defect of movement in it; the wound had 

 completely healed. 



2nd Operation, March 3. — Sixty days after the first operation. The 

 animal had recovered full use of right hand and arm ; the sole remaining 

 defect seemed a slight clumsiness of the digits, revealed by testing it in the 

 picking up of maize-grains, etc. But during the last previous eight days 

 it has seemed that the pose of the right hand when at rest indicates some 

 slight over-extension at the metacarpo-phalangeal joints. A second opera- 

 tion was now undertaken. The same region of the left hemisphere as in the 

 first operation was re-exposed. The dural flap was turned upward toward 



