2o8 Mayow 



There is certainly yet another use of respiration to 

 be looked for, one that makes it so necessary. And 

 what I have thought out on so obscure a matter I shall 

 shortly state. 



Life, if I am not mistaken, consists in the dis- 

 tribution of the animal spirits, and their supply is 

 most of all required for the beating of the heart and 

 the flow of blood to the brain. And it appears that 

 respiration chiefly conduces to the motion of the 

 heart in the manner to be stated elsewhere. For it is 

 probable that this aerial salt is altogether necessary 

 for every movement of the muscles ; so that without 

 it there could be no pulsation of the heart. 



For if it be allowed that the sudden contraction of 

 the muscles results frqm the intermixture of particles 

 of diff'erent kinds, mutually moving each other, then 

 it is scarcely to be supposed that the particles of both 

 kinds, by the effervescence of which the contraction of 

 the muscles is caused, proceed from the mass of the 

 blood ; for liquids derived from the same source re- 

 unite without any effervescence, so that it appears 

 that something extraneous is required for the pro- 

 duction of the motive fermentation. 



We may then suppose that nitro-saline particles 

 derived from the inspired air constitute the one kind 

 of motive particles, and that these, when they 

 meet the others, the saline-sulphureous particles 

 supplied by the mass of the blood and residing in the 

 motor parts, produce the effervescence from which 

 muscular contraction results, as will be shown more 

 fully in another place. 



And in fact motion is produced in the heart in no 

 different way than in the other muscles ; but I do not 

 think, for the reasons assigned above, that the motive 

 effervescence takes place in its ventricles but in its 



