186 



from four and a half to ^ of carbonic acid. The 

 air confined under the bed-clothes where different per- 

 sons had slept, he found likewise to contain from 

 four to of carbonic acid. In the stomach also, 

 carbonic acid is formed : and from that organ the 

 proportion of oxygen gas diminishes progressively 

 downwards, the carbonic acid varies in quantity, and 

 the nitrogen gas is uniformly increased *. These 

 experiments prove, that carbonic acid is produced 

 wheresoever the surfaces of the living body are 

 brought into contact with atmospheric air. 



148. Whence, then, does this carbonic acid pro- 

 ceed ? Dr Ingenhousz, finding that small bubbles of 

 air still escaped from the surface of the body, even 

 although he first carefully removed those which na- 

 turally adhered to it, was led to consider them as an 

 aerial transpiration from the skin ! But when Dr 

 Priestley employed rain water, from which the air 

 had been completely expelled by boiling, and detach- 

 ed also the adhering bubbles from his arm, he was 

 never able to collect a single bubble of air {. Dr 

 Pearson also found, that there was no appearance of 

 aerial bubbles on the surface of the cuticle during 

 bathing in warm water that had been previously 

 boiled, so as to expel the air usually mixed 

 with it. And M. Jurine, after remaining in the 

 bath for hours together, in temperatures varying 



* Mem. de la Societe de Med. torn. x. 



f Exper. sur les Vegetaux, torn. i. p. 152. 



J Experiments and Observations, vol. v. p. 103. 



Hunter's Observations on Animal (Economy, p. 168, 



