60 Borelli and the Influence [lect. 



" veins, one into each cavity of the heart. These drops of 

 " blood are then rarified, and all of a sudden filling up a space 

 "incomparably greater than that which they occupied before, 

 " press upon and close those little doors which guard the 

 " entrances to the veins, preventing by this means any more 

 " blood falling into the heart, and press upon and open the 

 "doors of the two arteries, into which they, the drops of blood, 

 " enter promptly and with force, thus making the heart and 

 " with it all the arteries of the body expand. But immediately 

 " afterwards this rarified blood is condensed once more or 

 " penetrates into other parts ; and thus the heart and arteries 

 "cease to be distended, the little doors which guard the en- 

 " trances to the two arteries close again, and those which guard 

 " the entrances to the two veins open again and give passage 

 " to two other drops of blood, which once more make the heart 

 "and arteries expand, just like those which went before." 



Such is Descartes' dogmatic exposition of the working of 

 the heart. Rejecting Harvey's new conclusions, he takes his 

 stand on the old Galenic doctrine of the innate heat of the 

 heart, and of the expansion of the heart by that heat. But 

 indeed about these things he did not care much ; his mind was 

 set on the nervous system ; he was concerned with the circu- 

 lation only so far as this supplied the material basis of nervous 

 energy. He only sought to explain how the blood, itself 

 derived from the food, gave rise to those animal spirits by means 

 of which the special earthly machine, the brain with its nerves, 

 carried out the behests of the rational soul. He thus explains 

 how the best part of the blood is carried to the brain for the 

 purpose of generating the animal spirits : 



" The most agitated and vivified parts of the blood, being 

 "carried to the brain by the arteries which spring from the 

 " heart in the most direct line, constitute as it were a very 

 "subtle air or wind, called the animal spirits, which dilating 

 " the brain fit it to receive the impressions of external objects 

 " and also those of the soul, that is to say, fit it to be the seat 

 "of common sensation, of imagination, and of memory. This 

 " air or these spirits then flow from the brain along the nerves 

 "into all the muscles, whereby they dispose the nerves to 



