216 JOSEPH DUERSON STOUT 



,eat 37. From the stimulation of each of these fields positive 

 motor results were obtained, though differing considerably, both 

 in degree and in nature, for even successive tests of the same 

 pair of points in the motor and extra-motor regions. 



While in general the results have exhibited only controlling 

 or steadying action by the simultaneous extra-motor stimula- 

 tion, it should be mentioned that some of the results indicate the 

 possibility, or even probability, of an augmenting influence by 

 the addition of such an extra-motor stimulus. An example of 

 such effect is presented in the tracing of the myogram for the 

 stimulation applied to two such points on the cortex of cat 36, 

 as shown in figure 67. 



There is frequently a retardation of the muscular relaxation 

 when there is present, or there is added, an extra-motor stimu- 

 lation during the period immediately following the discontinu- 

 ance of the stimulus to the motor cortex (figs. 63, 64, and 65). 

 The addition of the extra-motor stimulus also frequently results 

 in a decrease of clonic activity, resulting from the continuance 

 of a motor stimulus (figs. 63, 66, and 68). The addition of, or 

 the presence of, an extra-motor stimulus was never found to 

 cause an abnormal continuance of activity initiated by a stimu- 

 lation applied to a point within the motor cortex, although it 

 was usually able to cause a retardation of the relaxation time, 

 when the motor current was discontinued. In nearly all cases, 

 the curves showed a commencing relaxation immediately fol- 

 lowing the removal of the motor current, even though a com- 

 paratively strong current was applied to some point of the 

 extra-motor cortex. 



A satisfactory explanation for the influence of the stimulation 

 of the extra-motor regions, upon the activity of the motor re- 

 gions, is not at hand. The actual explanation cannot be definitely 

 stated until further work on the nervous system has been done, 

 and until some of the at present imperfectly understood con- 

 nections are definitely learned. It may, however, be stated that 

 the exertion of an inhibiting, exaggerating, or steadying influ- 

 ence can be accounted for in one of several ways: (a) the extra- 

 motor areas may exert such influence by direct connections with 



