190 Ley ton and Sherrington 



index of left hand, and very little ability, although some, to move the 

 three ulnar digits. The animal seemed imperfectly aware of where his 

 thumb and index actually might be. Yet in climbing about his cage he 

 hooked on to the bars with the ulnar fingers of left hand curved to a 

 rather open claw. The wrist was clearly " dropped " ; at elbow and at 

 shoulder there was little obvious impairment. Next day there was distinct 

 improvement in the motility of left hand and wrist. There was less wrist- 

 drop, and the index finger was seen to be moved at times. The animal was 

 in o-ood general condition, and climbed actively about the cage. It was 

 therefore determined to ablate more of the arm area of right hemisphere. 



4th Operation, April 3. — The animal was again put under deep 

 narcosis, and the central gyri of the right hemisphere were exposed for 

 the middle portion of their length. The cortex of precentralis was found 

 excitable down to the very margin of the area extirpated the da}^ before. 

 From a point in the arm area close above the extirpation, field movement 

 of little finger was obtained by strong faradisation ; this was a primary 

 movement of the little finger unaccompanied by movement elsewhere. 

 From arm area close above the extirpation, field movement of other fingers, 

 and slightly of thumb and index, was also obtained, but always as a 

 secondary movement, never as a leading or primary one. " Epilepsy " of 

 arm when provoked sometimes spread to the ulnar fingers, but never to 

 thumb or index. The area of yesterday's extirpation was itself tested by 

 thrusting the electrode 10 mm. into it ; the electrode, though buried in clot, 

 must have reached the floor of the ablation hole, and movements of thumb 

 and index were then obtained, but were very weak and uncertain. Out- 

 side the lesion area the precentralis was found, as on the previous day, to 

 present a continuous excitable field. From the post-centralis, as yesterday, 

 no responsive movement was obtainable. A map was made, fixing the 

 topography of a number of the excited points in precentralis. The area of 

 cortex indicated on the figure as bounded by fissura centralis and the dotted 

 line above (fig. 5, B, limit line marked 3, iv.,) was then excised to the same 

 depths as yesterday. After this ablation the cortex of precentralis above 

 the freshly ablated piece was tested with faradisation and found to be still 

 excitable down to its very edge, but from it shoulder movements only were 

 elicitable, and there occurred no " march " or spread of the movement to 

 other portions of the limb. 



On recovering from the operation narcosis the animal exhibited marked 

 wrist-drop, more so than yesterday ; but active movements of the wrist 

 were noticed to occur from time to time. The ulnar fingers were not so 

 successfully moved as before the operation, though they were still slightly 

 moved at times. A little movement was still observed occasionally in 

 thumb and index. Using the ulnar edge of hand with its partially 

 flexed ulnar fingers as a sort of claw, the animal conveyed a grape-berry 

 from the hand oflering it to its own lips. Its lips took it with difficulty, 

 because the pronated hand came with its radial edge toward the mouth, 



