OXIDATIONS INTO UEIC ACID AND UREA. 143 



(i 50.) But we are actually concerned with a comparison of the 

 amounts of heat evolved in the oxidation of tissue-carbon into 

 the solid carbonic oxide constituent of uric acid on the one hand, 

 . and into the gaseous carb-anhydride discharged from the lungs 

 on the other. Now it would appear that the latent heat of gaseous 

 carbon, or the quantity of heat absorbed in its vaporisation, 

 amounts to fully - of that evolved by its mere combustion into 

 carb-anhydride ; * so that the ratio of the heat evolved by the 

 combustion of carbon into gaseous carb-anhydride CO 2 , to the 

 heat evolved by its combustion into solid carbonic oxide CO, would 

 be as | to l - (more exactly as -^ to j^), or of course as i to ^ 

 even leaving out of consideration the probable excess of heat 

 developed in the production of solid carbonic oxide over that 

 developed in its conversion into solid carb-anhydride. By the dis- 

 charge, then, of uric acid, instead of carb-anhydride and urea, 

 there is a loss of 50 per cent, of heat by imperfect oxidation, 

 minus a gain of 25 per cent, of heat by the discharge from the 

 body of solid carbon and oxygen in the form of uric acid, instead 

 of gaseous carbon and oxygen in the form of carb-anhydride. 



I am aware that in arriving at this conclusion, which is avowedly 

 based on assumption, several modifying actions of more or less 

 importance have been disregarded ; still I think it cannot be 

 doubted that the amount of heat produced by the conversion of 

 tissue-carbon into the carbonic oxide constituent of uric acid is 

 more nearly | than J of that produced by its conversion into 

 gaseous carb-anhydride. Moreover, the amount of oxygen con- 

 sumed in the production of carbonic oxide being only one-half of 

 that consumed in the production of carb-anhydride, the amount 



* While 12+16 grammes of carbonic oxide CO, in uniting with 16 

 grammes of oxygen 0, evolve 68 units of heat, 12 grammes of carbon C, 

 in uniting with twice 16 grammes of oxygen O a , evolve not 136, but only 

 96 units of heat; the difference between 136 and 96, or 40 units of heat, 

 being absorbed in changing the 1 6 grammes of carbon from the solid to the 

 gaseous state. This calculation leaves out of consideration the heat absorbed 

 and evolved respectively, in the conversion of one volume of oxygen into 

 two volumes of carbonic oxide, and of two volumes of carbonic oxide plus 

 one volume of oxygen into two volumes of carb-anhydride. 



