On Muscular Motion and Animal Spirits 255 



will not be transmitted to the brain for the prepara- 

 tion of animal spirits, and therefore the animal will 

 speedily die. 



From these things I conclude that it is to some 

 extent made out that nitro-aerial particles, transmitted 

 by means of respiration to the mass of the blood and 

 thence to the brain, are the animal spirits themselves. 

 And this is in accordance with the fact that animals 

 placed in a glass vessel from which the air is exhausted 

 by means of Boyle's air-pump, after a short time 

 perish miserably in convulsions. For the animal 

 spirits being deprived, by the removal of the air, of 

 their due supplement, enter, as is their wont, upon 

 disorderly movements, and rushing tumultuously into 

 the nervous system, excite convulsive movements, 

 and at last the animal dies for want of air and of 

 spirits. 



To these things I further add that those who suffer 

 from English consumption are very much weakened 

 and are almost destitute of animal spirits. And the 

 reason of this seems to be, that as their lungs are 

 wasting and flaccid, the nitro-aerial spirit is no longer 

 brought to the mass of the blood in quantity sufficient 

 for the preparation of animal spirits. 



Nor should it be overlooked that in pestilential 

 diseases the brain chiefly suffers, and the economy 

 of the animal spirits is disturbed : for in so far as, in 

 the spread of the plague, the nitro-aerial spirit is 

 tainted by the poison, it must follow that the animal 

 spirits, composed of it, are out of sorts. 



At any rate nitro-aerial particles seem to be in the 

 highest degree suitable for the preparation of animal 

 spirits ; for it is the nature of spirits to be sometimes 

 inert and languid, and indeed on the other hand 

 sometimes very active and agile. Similarly the nitro- 



