155 



so that the weight of the carbonic acid exceeded that 

 of the oxygen gas by 2059.23 grains. This excess 

 must be attributed to the addition of carbon (119.) 

 derived from the animal system ; and which makes 

 it to constitute ^ of the weight of the acid that is 

 formed. In the experiments of Mr Davy (122.), 

 the volume of oxygen gas that disappeared every 

 minute, was 31.6 cubic inches, and that of carbonic 

 acid produced 26.6 inches. But one cubic inch of oxy- 

 gen gas weighs 0.3474 of a grain, and therefore 31.6 

 cubic inches will weigh 10.97784 grains : and again, 

 one cubic inch of carbonic acid weighs 0.467 of a 

 grain, and therefore 26.6 inches will weigh 1 2.4222 

 grains : so that the weight of the carb -nic acid ex- 

 ceeds that of the oxygen gas by 1.4444 grains, or 

 the carbon, as before, constitutes ~ of the com- 



o.o 



pound. From these facts, it would se^ m, that the 

 proportion of carbon, which composes the carbonic 

 acid of respiration, is much less than that which 

 forms the same acid in combustion, which, as we 

 before remarked (13.), was estimated by Guyton at 

 one-fifth. But the whole subject is, at present, sur- 

 rounded with so many difficulties, that nothing more 

 can be expected than an approximation to the truth ; 

 and we must content ourselves, therefore, with sta- 

 ting generally, that, although the carbonic acid 

 formed in respiration be less in bulk than the oxy- 

 gen gas which disappears, yet that it much exceeds 

 it in weight ; and that this excess is derived from 

 the carbon supplied by the animal system. 



125. As the conversion of oxygen gas into car- 

 bonic acid is at all times going on in the lungs, du- 



