276 ARCHIVES OF XEUROLOGY AND PSYCHIATRY 



SUMMARY 



The greater part of the precentral gyrus of both hemispheres was 

 destroyed in monkeys which had been trained previously in habits of 

 manipulation and visual discrimination. When the animals recovered 

 from paralysis, it was found that they showed perfect retention of these 

 habits. From this it is concluded that the so-called motor areas are not 

 directly concerned with the performance of complex learned activities. 

 The motor impulses of conditioned reflexes must descend from other 

 areas of the cerebral cortex than the precentral gyri, and the latter 

 cannot be regarded as the source of impulses to "voluntary movements.'* 



Destruction of the corpus striatum subsequent to recovery from 

 diplegia produced only the usual symptoms of striate lesion without 

 recurrence of the symptoms of cerebral paralysis. Recovery from 

 paralysis was therefore not due to vicarious function of this nucleus. 



The evidence for considering the precentral gyrus as a part of the 

 kinetic mechanism for reflex control of spinal posture and for mainte- 

 nance of excitability of lower motor centers is summarized. 



