THE MOTOR CENTERS AND THE WILL. in 



Consider for a moment the passage of the nerve impulses through 

 the brain that would have to occur. At the outset we find that the 

 sensory perceptive centers would have to be engaged with two differ- 

 ent ideas at once ; but Lewes showed long ago that introspection tells 

 us this is impossible, that " consciousness is a seriated change of feel- 

 ings " : he might equally well have said ideas. And, again, we know 

 that when two streams of energy of like character meet, they mutually 

 arrest each other's progress by reason of interfering with the vibration- 

 waves. 



I will show directly that this is actually the case in the action of 

 the cortex when the above-mentioned dilemma is presented to it. The 

 experiment I have devised for this purpose is extremely simple. A 

 person who is more or less ambidextrous, and who has been accus- 

 tomed for a long time to draw with both hands, attempts to describe 

 on a flat surface a triangle and circle at the same moment. I chose 

 these figures, after numerous trials, as being the most opposite, seeing 

 that in a triangle there are only three changes of movement, while in 

 a circle the movement is changing direction every moment. To insure 

 the attempt to draw these figures simultaneously succeeding, it is ab- 

 solutely necessary that the experimenter should be started by a signal. 



When the effort is made, there is a very definite sensation in the 

 mind of the conflict that is going on in the cortex of the brain. The 

 idea of the circle alternates with that of the triangle, and the result 

 of this confusion in the intellectual and sensorial portions of the brain 

 is that both motor areas, though remembering, as it were, the determi- 

 nation of the experimenter to draw distinct figures, produce a like 

 confused effect, namely, a circular triangle and a triangular circle. If 

 the drawing is commenced immediately at the sound of the signal, it 

 will be found that the triangle predominates ; thus, if I determine to 

 draw a triangle with my left hand and a circle with my right, the tri- 

 angle (though with all its angles rounded off) will be fairly drawn, 

 while the circle will be relatively more altered, of course made trian- 

 gular. On the other hand, if the two figures are not commenced 

 simultaneously, it will be found that usually the one begun last will 

 appear most distinct in the fused result, in fact, will very markedly 

 predominate. 



Now, the course of events in such an experiment appears to be 

 clear. The idea of a triangle and circle having been presented to the 

 intellect by the sensory centers, the voluntary effort to reproduce these 

 is determined upon. Now, if we had a dual mind, and if each hemi- 

 sphere was capable of acting /j^r se, then we should have each intel- 

 lectual area sending a message to its own motor area, with the result 

 that the two figures would be distinct and correct, not fused. 



The other evidence that I referred to above, which is adduced in 

 favor of the synchronously independent action of the two hemispheres 

 is from the account of such cases as the following : Professor Ball, of 



