142 Ley toil and Sherrington 



responses trespassed actually into the area that had previously yielded 

 shoulder movements as the primary response. Here the " deviation of 

 response " was seen to affect a whole series oi" points, influencing in its 

 special direction a not inconsiderable fraction of the whole arm area. 



Aojain, in an experiment on a gorilla, a point 172 which had been 

 yielding regularly flexion of all Angers without thumb, on being stimulated 

 next after a point 142, which yielded extension of index finger alone, 

 yielded extension of index alone without movement of the other fingers 

 (fig. 12, A, points 172, 142). Later, when stimulated after an interval of 

 some two minutes, it yielded flexion of fingers as at first. 



Ao-ain, in the same experiment, a point 176, which yielded regularly 

 extension of fingers without thumb, on being stimulated in next succession 

 to point 172 yielded flexion of fingers instead of extension of them. It 

 was, however, not found possible by stimulating point 172 in next 

 succession to point 176 to obtain movement 176 from point 172. Further, 

 on stimulating the two points, by separate electrodes, concurrently it was 

 found that a stimulation of 172, weak as judged by the induction scale 

 and also by its nearness to threshold value of excitation, caused flexion 

 of fingers in spite of concurrent stronger stimulation of 176. Also an 

 extension of the fingers already brought about by stimulating 176 alone 

 was broken down and converted into flexion by weak stimulation then 

 applied to 172, although the stimulation of 176 was continued unremitted. 

 Indeed the extension of fingers produced by stimulation of 176 seemed 

 more readily broken down and changed to flexion by stimulation of 172 

 when the stimulation of 176 had been in progress for some little time than 

 when stimulation of 172 was introduced earlier. When, conversely, flexion 

 of fingers was in progress under stimulation of 172, the application of 

 strono-ish stimulation to 176 broke down the flexion and changed it to 

 extension; but for this the stimulation of 176 had to be strongish. Also 

 when the stimulation of 172 and 176 was commenced concurrently, but 

 the stimulation of 176 was strong and that of 172 very weak, the result 

 obtained was extension not flexion, that is, 176 overpowered 172. 



Again, we have in several hemispheres observed that a cortex point 

 which ordinarily evoked as its primary response flexion of the elbow 

 would evoke, when stimulated next and soon after a distant point giving 

 adduction of thumb, flexion of elbow and adduction of thumb. 



Again, on the opposite hemisphere of the same gorilla referred to above 

 a point 218, which yielded regularly flexion of wrist followed by flexion of 

 elbow, yielded on being stimulated after stimulation of a point 251 yield- 

 ing rotation of shoulder, rotation of shoulder and not flexion of wrist or 

 elbow. It yielded these latter, however, as secondary movements if the 

 stimulation were prolonged, and it yielded them again as its primary re- 

 sponse after a time interval had been allowed (fig. 12, B, points 218, 251). 



The distances across which " deviation of response " may be exerted by 

 one point on another vary. Though usually the space intervening between 



