rcct-if] s it more and more, ar.cl disposes it insensibly to 

 renew the nature of the aniniaL 



,5. Respiration comprehends two alternate motions; 

 one of inspiration, \vhich gives admittance to the air 

 within ; the oilier, oi- expiration, which, expels it, tilled 

 with the vupours of the animal. 



The lungs are the principal instrument of respiration. 

 They are principally formed of a collection of cartila- 

 ginous and elastic vessels, which after being divided and 

 sjibdi\ided into a prodigious number of branches?, meet 

 in different parts, and terminate at one or more common 

 trunks, called trachff?, or air-vessels, whose aperture is 

 on the reside of Hie body. The ramification.; of the 

 air-vessels "are connected with the- vessels of circulation, 

 .and accompany them in their pussage through the 

 lungs. 



6. The blood is that rich fund from whence nature 

 derives that diversity of materials she employs with so 

 much art in the const ruetiOB s of her wonderful edili< e, 

 T.h is, as it goes from the heart, meet?, here and there 

 -on its passage, with certain organical, and as it were 

 knotted ma>ses, in which it is deprived of part <v 

 principles. 



We f-:i:uiot yet penetrate the true merli;imsro of 

 ereiivns : we can only faintly perceive-, that tlicv ir.uy 

 operate by a gradual diuiinurion of the vessels w'siefi 

 j*roportiv.'ns them to (he sinailness of the .parlirlcs that 

 re to be separated. They may likewise bear some 

 ittiiiiity to the configuration of these particles, and favour 

 -the extraction of them by means of the slackening which 

 their folds and various circumvolutions occasion to the 

 circulation. Thus it is, that by causing the aliment to 

 JHI^S through an infinite number of strainers, nature is 

 enabled to assimilate it to the animal, and incorporate 

 it ii;to his ilesh. This is then neither chyle nor blood; 

 it is a much more refined liquor, and known by the 

 va^ue name of lymph. 



G 2 



