CHAP, ii.] THE BRAIN. 1047 



part than to distinguish the areas corresponding to the several 

 movements of that part. Hence the nomenclature usually adopted 

 in speaking of the motor region is one based on the parts of the 

 body moved rather than on the character of the movements. The 

 more closely however the movements in question are studied, the 

 more probable it appears that the localisation which obtains in 

 the cortex is essentially a localisation corresponding not to parts 

 of the body, or to nerves, or to muscles, but to movements. In 

 considering this point it must be remembered how rude and 

 barbarous a method of stimulation is that of applying electrodes 

 to the surface of the grey matter compared with the natural 

 stimulation which takes place during cerebral action; the one 

 probably is about as much alike the other, as is striking the keys 

 of a piano at a distance with a broomstick to the execution of a 

 skilled musician. Were it in our power to stimulate the cortex 

 in any way at all approaching the natural method, ^e should in 

 all probability arrive at two results; on the one hand we should 

 be able to produce at will a variety of movements of different 

 degrees of complexity, some very simple, others very complex, and 

 for these we should have to use names suggested by the characters 

 and purpose of each movement, and by these alone ; on the 

 other hand we should find very decided limits to the number and 

 kind of movements which we could evoke, limits fixed in the case 

 of each subject partly by inherited organisation, partly by the 

 training of the individual. 



Some such results of refined experimentation are indeed 

 already foreshadowed by the rude results of our present rough 

 methods. The movements which usually follow stimulation of 

 the motor region, and which we have described as flexion, &c., are, 

 so to speak, the elementary factors of ordinary bodily movements 

 the detached and imperfect chords of a musical piece ; and in the 

 following facts relating to their production we can recognize the 

 influences of organisation and habit. As we have said, stimulation 

 of the motor area of one hemisphere produces movements, as a 

 rule, which are limited to one side of the body, and that the 

 opposite side. Now both in ourselves and in the higher animals 

 a large number of bodily movements, especially of the limbs, are 

 habitually unilateral; and, putting aside the question why there 

 should be two halves of the brain, and why the one half of the 

 brain should be associated with the cross half of the bodily, we 

 may recognize in the unilateral crossed movement resulting from 

 stimulation of the cortex an accordance with natural habits. But 

 some movements of the body are ordinarily bilateral; the two 

 eyes, for instance, are ordinarily moved together, and the two sides 

 of the trunk move together very much more frequently than do 

 the two fore limbs or the two hind limbs. And in accordance 

 with this we find that stimulation of the motor area for the eyes 

 on either hemisphere produces movements of both eyes, and 



