1912.] 



Instability of Cortical Points. 



269 



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Fig. 1! 



Experiment 9, Macacus rhesus, 9.2.12. — In this record a cortical E point is twice 

 stimulated with an interpolated stimulation of the ipsilateral ulnar nerve. The first 

 E stimulus gives a good extension reaction. The ipsilateral ulnar nerve then gives a 

 flexion-reflex. At the second repetition of the E stimulus there is little movement in the 

 extensor tracing, and the state of maintained flexor contraction is not markedly 

 interfered with, there being only a transient- and small relaxation. This shows 

 depression of the E point reaction. 



causing relaxation of the flexor's contraction has increased that contraction, 

 although on being restimulated a few seconds after the cessation of the ulnar 

 reaction it has caused its usual flexor relaxation (fig. 16). 



Taken together, the effect of the stimulation of the ipsilateral afferent nerve, 

 which in the decerebrate preparation is to contract the flexor and inhibit the 

 extensor of its own limb's elbow, is with the cerebrum intact to augment 

 the action of the cortical point for elbow flexion and to reverse the action 

 of the cortical point for elbow extension to elbow flexion. This indicates 

 that the activity of the local peripheral afferents may be a factor of 

 importance in determining what one of us has termed the neural balance 



