144 Circulation of the Blood 



slices of the tissues, are to be regarded as so many 

 different aereal forms, or kinds of vapour. 



And here I would gladly be informed by those who 

 admit corporeal spirits, but of a gaseous or vaporous 

 consistency, in the bodies of animals, whether or not 

 they have the power of passing hither and thither, like 

 distinct bodies independently of the blood? Or whether 

 the spirits follow the blood in its motions, either as 

 integral parts of the fluid or as indissolubly connected 

 with it, so that they can neither quit the tissues nor 

 pass hither nor thither without the influx and reflux, 

 and motion of the blood ? For if the spirits exhaling 

 from the blood, like the vapour of water attenuated by 

 heat, exist in a state of constant flow and succession as 

 the pabulum of the tissues, it necessarily follows that 

 they are not distinct from this pabulum, but are in- 

 cessantly disappearing ; whereby it seems that they can 

 neither have influx nor reflux, nor passage, nor yet 

 remain at rest without the influx, the reflux, the passage 

 [or stasis] of the blood, which is the fluid that serves as 

 their vehicle or pabulum. 



And next I desire to know of those who tell us that 

 the spirits are formed in the heart, being compounded 

 of the vapours or exhalations of the blood (excited 

 either by the heat of the heart or the concussion) and 

 the inspired air, whether such spirits are not to be 

 accounted much colder than the blood, seeing that 

 both the elements of their composition, namely, air 

 and vapour, are much colder? For the vapour of 

 boiling water is much more bearable than the water 

 itself; the flame of a candle is less burning than the 

 red-hot snuff, and burning charcoal than incandescent 

 iron or brass. Whence it would appear that spirits of 

 this nature rather receive their heat from the blood, 

 than that the blood is warmed by these spirits ; such 

 spirits are rather to be regarded as fumes and excre- 

 mentitious effluvia proceeding from the body in the 

 manner of odours, than in any way as natural artificers 



