1912.] 



Instability of Cortical Points. 



•2(57 



tion after the peripheral nerve stimulation may produce relaxation instead of 

 contraction of the flexor muscle — that is, may shew reversal of its previous 

 action. Whether such reversal is referable to the epileptoid discharge 

 induced or to the influence of the precurrent peripheral nerve stimulation 

 remains, however, an open question. 



Turning to the influence of the peripheral nerve stimulation upon the 



Experiment 15, Callothrix, 5.2.12. — In this record a cortical point which was giving 

 primary flexion was stimulated (E — F), and during that stimulation another stimulus 

 (X — Y) was applied to the ipsilateral ulnar nerve. The cortical stimulus just before the 

 application of the nerve stimulus had produced a contraction of both the antagonists. 

 The effect of the nerve stimulus was to augment the contraction of the flexor and abolish 

 that of the extensor. 



response of the cortical E point, this influence has been marked in the case 

 of the ulnar nerve of the ipsilateral side. The stimulation of this nerve, while 

 reinforcing the action of the F point (cf. supra), seems to antagonise that of 

 the E point. Sometimes temporarily the reaction of the E point is practically 

 suppressed after the reaction from the ipsilateral ulnar nerve (fig. 15). Some- 

 times E's reaction is absolutely reversed ; this we have seen when during an 

 ipsilateral ulnar stimulation the E point has been excited and instead of 



Fig. 13. 



