226 KESPIRATION. 



i '17421 volumes of oxygen are absorbed from it: and 

 that when the average quantity of carbonic acid, 'I.e., 

 1346 cubic inches, or 636 grains, is exhaled in the hour, 

 the quantity of oxygen absorbed in the same time is 1584 

 cubic inches or 542 grains. According to this estimate, 

 there is more oxygen absorbed than is exhaled with carbon 

 to form carbonic acid without change of volume ; and to 

 this general conclusion, namely, that the volume of air 

 expired in a given time is less than that of the air inspired 

 (allowance being made for the expansion in being heated), 

 and that the loss is due to a portion of oxygen absorbed 

 and not returned in the exhaled carbonic acid, all observers 

 agree, though, as to the actual quantity of oxygen so ab- 

 sorbed, they differ even widely. 



The quantity of oxygen that does not combine with the 

 carbon given off in carbonic acid from the lungs, is pro- 

 bably disposed of in forming some of the carbonic acid 

 and water given off from the skin, and in combining with 

 sulphur and phosphorus to form part of the acids of the 

 sulphates and phosphates excreted in the urine, and pro- 

 bably also, from the experiments of Dr. Bence Jones, with 

 the nitrogen of the decomposing nitrogenous tissues. 



The quantity of oxygen consumed seems to vary much, 

 not only in different individuals, but in the same individual 

 at different periods ; thus it is considerably influenced by 

 food, being greater in dogs when fed on farinaceous than 

 on animal food, and much diminished during fasting, 

 while it varies at different stages of digestion. Animals 

 of small size consume a relatively much greater amount of 

 oxygen than larger ones. The quantity of oxygen in the 

 atmosphere surrounding animals, appears to have very 

 little influence on the amount of this gas absorbed by 

 them, for the quantity consumed is not greater even 

 though an excess of oxygen be added to the atmosphere 

 experimented with (Regnault and Eeiset). 



The Nitrogen of the Atmosphere, in relation to the respira- 



