214 JOSEPH DUERSON STOUT 



field, and what we believe are areas influencing the true motor 

 fields. In the present series of experiments, note was taken of 

 the comparative strengths of current and durations of stimula- 

 tion needed in the various areas investigated. It was found, as 

 previously mentioned, that from stimulation of points on the 

 cortex outside of the sigmoid area either a longer application or a 

 stronger current, or both, was required to obtain motor reac- 

 tion than for successful stimulation of the sigmoid or true 

 motor areas. 



THE EFFECT OF SIMULTANEOUS OR SUCCESSIVE STIMULATIONS AT 

 A MOTOR AND AN EXTRA-MOTOR POINT ON THE 

 CEREBRAL CORTEX 



On the brains of three animals there was investigated the 

 effect of stimulating a point in the motor region of the cortex 

 and, without discontinuing this stimulation, of adding a second 

 stimulation at some point on the extra-motor cortex. A kymo- 

 graphic record was taken of the responses, and the following 

 observations made : If a current of moderate strength is applied 

 to the motor areas, and this stimulus be continued for a time, a 

 clonic discharge is manifested in the appropriate muscles. If, 

 while continuing stimulation at the point within the motor cor- 

 tex, another current of similar strength is applied to some point 

 in the extra-motor cortex, the clonus is at once steadied to a 

 tonus (see figs. 63 and 68). Removal of the first current, while 

 continuing the second current, is at once followed by commencing 

 relaxation of the muscles involved, but the relaxation is very 

 much retarded by the presence of the extra-motor stimulation 

 (see fig. 65). In the relaxation following the removal of the 

 stimulus to the motor region, when this stimulus has alone been 

 applied, there is usually a slight tendency to after-movement. 

 The after effect is likewise present, but to a less degree, when 

 an extra-motor stimulus is kept applied, during the relaxation 

 stage (see fig. 63). 



The extra-motor stimulus, judging from these results, is able 

 to exert a steadying influence on the motor discharge, such as 



