182 DESCARTES' DISCOURSE ox METHOD n - 



erroneously ascribing the motion of the blood, not 

 to the contraction of the Avails of the heart, but to 

 the heat which he supposes to be generated there, 

 he adds : 



"This motion, which I have just explained, is as much the 

 necessary result of the structure of the parts which one can 

 see in the heart, and of the heat which one may feel there with 

 one's fingers, and of the nature of the blood, which may be 

 experimentally ascertained ; as is that of a clock of the force, 

 the situation, and the figure, of its weight, and of its wheels." 



But if this apparently vital operation were ex- 

 plicable as a simple mechanism, might not other 

 vital operations be reducible to the same cate- 

 gory ? Descartes replies without hesitation hi the 

 affirmative. 



" The animal spirits," says he, " resemble a very subtle fluid, 

 or a very pure and vivid flame, and are continually generated in 

 the heart, and ascend to the brain as to a sort of reservoir. 

 Hence they pass into the nerves and are distributed to the 

 muscles, causing contraction, or relaxation, according to their 

 ([iiantity. " 



Thus, according to Descartes, the animal body 

 is an automaton, which is competent to perform 

 all the animal functions in exactly the same way 

 as a clock or any other piece of mechanism. As 

 he puts the case himself : 



" In proportion as these spirits [the animal spirits] enter the 

 cavities of the brain, they pass thence into the pores of its 

 substance, and from these pores into the nerves ; where, accord- 

 ing as they enter, or even only tend to enter, more or less, into 

 one than into another, they have the power of altering the figure 



