222 ANIMAL AUTOMATISM. 



" But as regards the souls of beasts, although this is not the 

 place for considering them, and though, without a general exposi- 

 tion 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 orgaus and instruments by means of which the very same 

 movements would be accomplished in a machine. So that, even in 

 us, the spirit, or tho 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 lite 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 deter- 

 mines 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. 



u 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 disposi- 

 tion 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 are discoverable), and 

 then it will easily be seen, that all the actions of beasts are similar 



