239 



nute, 36 cubic inches, or 51840 cubic inches in the 

 space of a day, equal in weight to 3.9697 lb. troy. 

 But for every pound of carbonic acid formed by 

 the combustion of charcoal, a quantity of heat is 

 given out, according to Lavoisier, sufficient to melt 

 27.02024 lb. of ice : therefore, 3.9697 lb. of this 

 acid, produced daily in respiration, will furnish heat 

 enough to melt 107.2 lb. of ice ; for 27.02024 x 

 3.9697 107.2622. Of this quantity of heat, 

 however, a portion, adds Dr Menzies, is carried off 

 in the form of sensible heat with the air that is ex- 

 pired, and another portion is rendered latent by 

 combining with the vapour that issues from the 

 lungs. These two portions, from experiment, be 

 calculates to amount to heat sufficient to melt 

 32.9833 lb. of ice ; which sum, subtracted from 

 107.2622, leaves a remainder of 74.2789 lb. as the* 

 quantity of ice capable of being dissolved by the 

 heat daily set free, by the decomposition of the air, 

 in the lungs of an ordinary man *. How admirably 

 the blood in the lungs is disposed to receive this 

 heat, the vast extent of the cellular surface (114.) 

 of those organs, and the decomposition of the air, 

 and consequent extrication of its heat, going on 

 over every point of that surface, furnish abundant 

 proof. 



194. The inferences drawn from the foregoing 

 experiments and calculations appear to be just, if 

 the premises on which they are founded be in all 

 respects correct : but neither the quantity of air ta- 



Menzics on Respiration, p. 50. et seq-, 



