IX.] ANIMAL AUTOMATISM. 211 



After recapitulating the manner in which sensory 

 impressions transmitted by the sensory nerves to the 

 brain give rise to sensation, he proceeds : 



" And in addition to the different feelings excited in the 

 soul by these different motions of the brain, the animal spirits, 

 without the intervention of the soul, may take their course 

 towards certain muscles, rather than towards others, and thus 

 move the limbs, as I shall prove by an example. If some one 

 moves his hand rapidly towards our eyes, as if he were going to 

 strike us, although we know that he is a friend, that he does it 

 only in jest, and that he will be very careful to do us no harm, 

 nevertheless it will be hard to keep from winking. And this 

 shows, that it is not by the agency of the soul that the eyes 

 shut, since this action is contrary to that volition which is the 

 only, or at least the chief, function of the soul ; but it is because 

 the mechanism of our body is so disposed, that the motion of 

 the hand towards our eyes excites another movement in our 

 brain, and this sends the animal spirits into those muscles which 

 cause the eyelids to close." 



Since Descartes' time, experiment has eminently 

 enlarged our knowledge of the details of reflex action., 

 The discovery of Bell has enabled us to follow the 

 tracks of the sensory and motor impulses, along dis- 

 tinct bundles of nerve fibres; and the spinal cord, 

 apart from the brain, has been proved to be a great 

 centre of reflex action ; but the fundamental concep- 

 tion remains as Descartes left it, and it is one of the 

 pillars of nerve physiology at the present day. 



V. The motion of any given portion of the matter 

 of the brain excited by the motion of a sensw*y 

 nerve, leaves behind a readiness to be moved 

 in the same way, in that part. Anything 

 which resuscitates the motion gives rise to the 



