iv DESCARTES' DISCOURSE ON METHOD 183 



of the muscles into which the nerves are inserted, and by this 

 means of causing all the limbs to move. Thus, as you may have 

 seen in the grottoes and the fountains in royal gardens, the force 

 with which the water issues from its reservoir is sufficient to 

 move various machines, and even to make them play instru- 

 ments, or pronounce words according to the different disposition 

 of the pipes which lead the water. 



"And, in truth, the nerves of the machine which I am 

 describing may very well be compared to the pipes of these 

 waterworks ; its muscles and its tendons to the other various 

 engines and springs which seem to move them ; its animal 

 spirits to the water which impels them, of which the heart is the 

 fountain ; while the cavities of the brain are the central office. 

 Moreover, respiration and other such actions as are natural and 

 usual in the body, and which depend on the course of the spirits, 

 are like the movements of a clock, or of a mill, which may be 

 kept up by the ordinary flow of the water. 



" The external objects which, by their mere presence, act upon 

 the organs of the senses ; and which, by this means, determine 

 the corporal machine to move in many different ways, according 

 as the parts of the brain are arranged, are like the strangers 

 who, entering into some of the grottoes of these waterworks, 

 unconsciously cause the movements which take place in their 

 presence. For they cannot enter without treading upon certain 

 planks so arranged that, for example, if they approach a bathing 

 Diana, they cause her to hide among the reeds ; and if they 

 attempt to follow her, they see approaching a Neptune, who 

 threatens them with his trident : or if they try some other way, 

 they cause some other monster, who vomits water into their faces, 

 to dart out ; or like contrivances, according to the fancy of the 

 engineers who have made them. And lastly, when the rational 

 soul is lodged in this machine, it will have its principal seat in the 

 brain, and will take the place of the engineer, who ought to be 

 in that part of the works with which all the pipes are connected, 

 when he wishes to increase, or to slacken, or in some way to 

 alter their movements." 1 



1 Traite de I'Hommc (Cousin's edition), p. 347. 



