1884.] on the Physiological Aspect of Mesmerism. 29 



whether, for example, visual sensation and ideas are accompanied by 

 an activity of one part of the cortex, and auditory sensation and ideas 

 are accompanied by an activity of a different part of the cortex ; or 

 whether visual and auditory sensation and ideas may occur in any 

 part of the cortex, the mode of activity of the cells being different in 

 the two cases. 



Happily, it is not necessary to enter into this question in order to 

 gain a fair idea of the chief features of mesmerism. The idea which 

 we gain lacks no doubt definiteness in detail, and we must be prepared 

 to express it in different language according as we find later, that the 

 cortex of the cerebral hemispheres consists of one nerve centre with 

 many functions, or of many nerve centres with different functions, or 

 again as we find — and this is most probable — that the truth is between 

 these two extreme theories. 



But whilst we may put in the background the question of localisa- 

 tion of function for the cortex of the brain, we must linger a little to 

 consider its mode of action. I will take a particular instance. 



The changes which occur in the retina of the eye when rays of 

 light from an external object fall upon it give rise to nervous impulses 

 which eventually produce in the cortex of the brain a certain activity ; 

 this activity leads to our forming an idea of the object. Now in 

 some cases the formation of the idea is all that takes place : often, 

 however, impulses are sent out from the active cells of the cortex to 

 a motor centre in the lower part of the brain, and a movement is 

 made. This is a reflex action from the cerebral cortex. Here the 

 active sensory centre excites a motor centre, just as happens in the 

 spinal cord of a frog the leg of which is pinched. Our actions are 

 often of this nature, though in many cases of course it is very difficult to 

 say how far the will is exercised in the action. If you give a child 

 a sweetmeat, the child sometimes no doubt deliberates what to do with 

 it ; in others the rapid transference of the sweetmeat to the mouth 

 seems to be simply a reflex action entirely independent of any effort 

 of will, though accompanied by consciousness. 



Dr. Carpenter has introduced the useful term unconscious cerebra- 

 tion into physiological-psychology. By this is meant that the cortex 

 may be active without our knowing anything about it. An instance 

 which Dr. Carpenter gives, is that of trying to remember a name 

 which for the moment we have forgotten, in such cases it is often 

 best to give up consciously thinking, but the fundamental activities 

 in the brain which accompany thinking go on nevertheless, so that 

 presently without farther conscious effort, the name is remembered, is 

 as it were thrown up into consciousness. 



I said a moment ago that reflex actions not infrequently occur in 

 which a conscious idea forms part of the reflex chain. But conscious- 

 ness is not necessary to the reflex action ; that is, the changes in the 

 cortex which are the physical basis of the idea may be carried out 

 without giving rise to consciousness. Here we want a term to imply 

 that state in which everything necessary for an idea is present except 



