IX.] ANIMAL AUTOMATISM. 215 



place for considering them, and though, without a general 

 exposition of physics, I can say no more on this subject than I 

 have already said in the fifth part of my Treatise on Method ; 

 yet, I will further state, here, that it appears to me to be a very 

 remarkable circumstance that no movement can take place, either 

 in the bodies of beasts, or even in our own, if these bodies have 

 not in themselves all the organs and instruments by means of 

 which the very same movements would be accomplished in a 

 machine. So that, even in us, the spirit, or the soul, does not 

 directly move the limbs, but only determines the course of that 

 very subtle liquid which is called the animal spirits, which, 

 running continually from the heart by the brain into the muscles, 

 is the cause of all the movements of our limbs, and often may 

 cause many different motions, one as easily as the other. 



"And it does not even always exert this determination; for 

 among the movements which take place in us, there are many 

 which do not depend on the mind at all, such as the beating of 

 the heart, the digestion of food, the nutrition, the respiration, 

 of those who sleep ; and, even in those who are awake, walking, 

 singing, and other similar actions, when they are performed 

 without the mind thinking about them. And, when one who 

 falls from a height throws his hands forwards to save his head, 

 it is in virtue of no ratiocination that he performs this action ; 

 it does not depend upon his mind, but takes place merely 

 because his senses being affected by the present danger, some 

 change arises in his brain which determines the animal spirits 

 to pass thence into the nerves, in such a manner as is required 

 to produce this motion, in the same way as in a machine, and 

 without the mind being able to hinder it Now since we observe 

 this in ourselves, why should we be so much astonished if the 

 light reflected from the body of a wolf into the eye of a sheep 

 has the same force to excite in it the motion of flight ? 



" After having observed this, if we wish to learn by reasoning, 

 whether certain movements of beasts are comparable to those 

 which are effected in us by the operation of the mind, or, on the 

 contrary, to those which depend only on the animal spirits and 

 the disposition of the organs, it is necessary to consider the 

 difference between the two, which I have explained in the fifth 

 part of the Discourse on Method (for I do not think that any others 



