AUTOMATIC MOVEMENTS. 167 



sensations which at first guided them, in such a manner that the 

 latter at last come to be in themselves adequate excitors of 

 the movement, when the series has once been commenced by 

 an exertion of the will. It has been thought by some a sufficient 

 proof of the voluntary nature of these movements, that we can 

 check them at any time by an effort of the will ; but this we do 

 only when the attention has been recalled to them, so that the 

 cerebrum, liberated, as it were, from its previous self-occupation, 

 resumes its usual play upon the automatic centres. It has been 

 asked, moreover, why, if these sensations are adequate to call 

 forth automatic movements when the perceptive and voluntary 

 operation of the cerebrum is suspended, they do not exert the 

 same influence when it is in its ordinary condition of functional 

 activity. This inquiry, however, is equally applicable to the 

 most undoubted cases of automatic movement ; thus we do not 

 find that tickling the soles of the feet in man ordinarily produces 

 the same semi-convulsive agitation of the lower extremities, that 

 such irritation will call forth when the spinal cord has been 

 divided or seriously injured in the dorsal region. And when 

 the cerebral influence is withdrawn by the absorption of the 

 mind in reverie, slight stimuli will often call forth unaccustomed 

 and sometimes powerful automatic movements. So, again, during 

 sleep, when both the cerebrum and the sensory ganglia are in a 

 state of torpor, reflex actions may be excited through the spinal 

 cord, such as could not be called forth by the same stimuli in the 

 waking state. The fact appears to be that, when the cerebrum 

 is in its usual state of activity, any irritation which would dispose 

 to reflex action, if its effect were limited to the automatic centres, 

 is expended (as it were) by being propagated onwards to the 

 cerebrum ; and the mind thus rendered conscious of it, controls, 

 if necessary, any tendency to automatic action which it may have 

 excited. But when this onward propagation of the polar state is 

 checked, either by interruption of the structural continuity, or by 

 the want of a recipient condition of the cerebrum, it must then 

 react in the automatic apparatus itself. The case, in fact, appears 

 to us to be analogous to that of the emotional impulses, which 

 are not so prone to act upon the mi/id when they can discharge 

 themselves through the /^odj by muscular movement. The im- 



