218 ANIMAL AUTOMATISM. 



Nothing can be clearer in statement, or in illustra- 

 tion, than the view of reflex action which Descartes 

 gives in the "Passions de 1'Ame," Art. xiii. 



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 mus- 

 cles, 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 en- 

 larged 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 distinct bun- 

 dles 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 conception remains as Des- 

 cartes left it, and it is one of the pillars of nerve physi- 

 ology at the present day. 



Y. The motion of any given portion of the matter of the 

 brain excited by the motion of a sensory nerve , leaves 



