The Kxcitable Cortex of the Chimpanzee, Oranij-rtan, and (ioiilla 191 



the berrv Ivinc; at thi' far end of a short cone formed hv the claw-like 

 hand taperinj; to its ulnar t'dj:t.'. Kllxjw seemed sljijhtly defective in motor 

 power. Distinct, though slight, impairment of motor power was noted at 

 shoulder. There was not any trace of recrude.scence of paresis of the 

 right arm. 



Next morning considerable improvement was obvious in the motility 

 of left arm. Klbow and shoulder were no longer noticeably affected. 

 The arm was used fairly well for swinging from the roof of the cage. It 

 was clear tliat the ulnar Hnirers were used fairly well in willed movements. 

 Wrist-drop was severe, and seemed (juite as marked as yesterday afternoon. 

 Two days later the left arm had improveil further. Thumb and index 

 were evidently better and more freely employed. The animal when induced 

 to put forward its left arm for fruit, etc., offered to it does so by thrusting 

 the arm fairly skilfully, though with seeming hesitation and some eflfort, 

 between the cage bars. The paretic wri.st is prone. The grape-berry is 

 taken by the three ulnar fingers, more Hexed than formerly, assisted now 

 by the index : the thumb also was often moved in the manoeuvre, but did 

 not practically assist. 



April 7. — Further improvement in motility of left arm. Since the 

 right cortex operation, which impaired the motility of left arm, the motility 

 of right arm has notably increased, and right arm has been much more 

 frequently employed than before. No paresis remains detectable in it: 

 and hand, and the whole arm, are now repeatedly emplo^'ed for all their 

 usual purposes. This morning, after its breakfast, the animal sat and 

 picked its teeth with the isolatedly extended index finger of right hand. 

 It was seen also to pick and scoop out the furrows of the pinna of the 

 left ear with riorht index finorer. When making an efibrt to take with the 

 left hand a small object, e.g. maize-grain, there occurs frequently an 

 accompanying strong contraction (flexion) of the fingers of right liand. 

 The converse has not been noticed to occur. 



April 8. — Further improvement in motility of left arm, less wrist-drop, 

 better movement of index and thumb. 



5th Operation, April 8. — Under deep narcosis the arm area and the 

 circumjacent cortex of left hemisphere w^as laid bare. Gyrus post-centralis 

 was then tested by faradisation to see if, especially at the levels opposite 

 the excised portion of arm area, it had acquired motor responsiveness to 

 the electric stimuli, but no motor responses could be elicited from it. From 

 precentralis above the lesion, from the edge of the lesion right up to the 

 trunk area, between arm area and leg area, repeated excitation elicited, and 

 elicited easily, movements of shoulder, but of no other part of arm. Move- 

 ments thus evoked in shoulder were never on any occasion accompanied by 

 or followed by movements of elbow, wrist, fingers, or thumb. " Epilepsy " 

 was frequently obtained, but remained confined to shoulder, never spreading 

 to other parts of the limb. A map was made recording the topography of 

 a number of points at which carefully observed movements were evoked. 

 VOL. XL, NO. 2.— 1917. " 13 



