118 



sorbed from the air-cells instead of their transparent 

 fluid *. Does the air also, which is supposed to 

 pass out of the cells of the lungs into the blood-ves- 

 sels by a process of absorption, take the route of 

 these absorbent vessels ? To this question we reply, 

 in the language of Haller, that the fineness of those 

 vessels, the mucus perpetually smearing the surface 

 of the cells, the elastic nature of air itself, and its 

 repulsion by water, so that it neither penetrates moist 

 paper, cloth, nor skin, all demonstrate that no air 

 by this route gets into the blood |. If, indeed, air 

 were taken in by the absorbents, it must, as Dr 

 Goodwyn observes, take the route of those vessels, 

 and, by passing directly to the right side of the 

 heart, change the colour of the blood there ; which, 

 however, does not happen J : nor, when air was 

 forced down the windpipe of a dog, in the experi- 

 ments of Dr Hales, was it able to pass into the pul- 

 monary artery or veins ||. 



96. If, then, no proof exist of the passage of air 

 into the blood by the ordinary course of the absorb- 

 ent vessels, the only other mode of effecting this 

 purpose that has been hitherto suggested, is the 

 power of chemical affinity. What then are the che- 

 mical affinities subsisting between venal blood and 

 atmospheric air ? About the middle of the 17th cen- 

 tury, Dr Lower observed, that the upper surface of 



* On the Absorbents, p. 42. 



f Prim. Lineae, par. 306. 



J Connexion of Life with Respiration, p. 



H Statical Essays, vol. ii. p. 276. 



