MOTOR FUNCTIONS OF CEREBRAL CORTEX OF CAT 227 



exert influence on the respiratory movements. The anterior 

 portion of the field, adjacent to the motor field, gives move- 

 ments of the face, hind leg and fore ankle. These are similar 

 to the results of stimulation applied to the cortex within the 

 adjacent motor field, and it may be thought that overflow of 

 current into the motor cells might have been the cause of such 

 reactions, but the occurrence of motor reactions of the face from 

 the immediately adjacent field tends to discredit this, because 

 the portion of the motor field which controls activity of the 

 muscles of the face does not extend over this portion of the 

 cortex, but is confined to that region lying mainly in front of the 

 crucial sulcus. 



Simultaneous and successive stimulation of two different parts 

 of cortex. The application of two stimulations to the cortical 

 surface, one within the limits of the motor field, and the other at 

 some point on the cortex outside of the motor field, discloses the 

 following facts. 



17. If the motor current be applied first the muscular con- 

 tractions usually assume a clonic form. If the extra-motor cur- 

 rent be then applied, while continuing the motor current, the 

 clonus is sometimes steadied to a tonus. If the motor current 

 be now discontinued the phase of relaxation at once sets in, but 

 is much prolonged as compared with the relaxation following 

 the removal of stimulation applied to the motor cortex alone. 



18. The stimulation of a point within the extra-motor area 

 may be said to cause this area to exert a steadying influence on 

 the motor discharge from stimulation of the motor field, so long 

 as stimulation of the motor area is continued, but when stimu- 

 lation of the motor field is discontinued the extra-motor stimula- 

 tion is unable to cause a continuance of the motor discharge at 

 full force for even a brief period. The influence of the extra 

 motor-field is possibly such as to cause the motor discharge to 

 assume a more purposeful nature. 



Cortical and subcortical reactions. From comparison of the 

 motor reactions from stimulation of the motor cortex at various 

 points, and the reactions following the removal of small pieces 

 of the cortex at these same points, and subsequent stimulation 



