1016 RESPIRATION OF ANIMALS. 



accurate observations of Professor Magnus on the gases of the 

 blood, it appears that blood gives out from one tenth to one 

 eighth of its bulk of gas when placed in vacuo ; that the gas 

 obtained from both arterial and venous blood contains nitrogen, 

 oxygen and carbonic acid ; but that while the oxygen in venous 

 blood is at most from one fourth to one fifth of the volume of 

 the carbonic acid, the oxygen in the arterial blood equals at 

 least one third and sometimes almost half of the volume of the 

 carbonic acid in the same blood.* The solvent power of the 

 serum of the blood of the ox, for carbonic acid was found, 

 by M. Scherer, to be double that of pure water ; the serum 

 dissolving twice its bulk of carbonic acid, while water dis- 

 solves only an equal bulk of that gas, at the usual tempera- 

 ture of the atmosphere. 



The air of an easy expiration amounts to 15 or 18 cubic 

 inches, and contains about 3 4 percent of carbonic acid. The 

 air of a deep expiration contains 6 or 8 per cent of that gas, and 

 will not support the combustion of a candle. According to 

 Mr. Coathupe, the quantity of air which passes through the 

 lungs of a man of ordinary size, in twenty- four hours, is 266? cu- 

 bic feet, of which 204 cubic feet are changed into carbonic acid.f 

 The quantity of carbon thus thrown off daily from the system is 

 considerable, and is found by M. Liebig to be in proportion to 

 the animal heat evolved and exercise taken, and thus varies con- 

 siderably in different individuals. The proportion of carbon ex- 

 pired by himself is 6j ounces daily, by a soldier 13| ounces, by 

 prisoners in close confinement 7 ounces, and by a boy who takes 

 considerable exercise 9 ounces. In an experiment made on a 

 large scale, in which the quantity of carbon in the food and 

 also in the excrements and urine of 856 soldiers was ascer- 

 tained and compared, it was found that the carbon of the latter 

 amounted only to one twenty-seventh part of the carbon of the 

 former; and consequently twenty-six twenty-sevenths of the 

 whole carbon in the food was converted into carbonic acid and 

 discharged by the lungs. 



When the expired air of man and birds is examined, the pro- 

 portion of oxygen which has disappeared has generally been found 

 sensibly the same as that of the carbonic acid produced ; while it 



* Annales de Chimie et de Physique, t. 65, p. 182. 

 t Phil. Mag. 3rd Ser. v. 14. p. 401. 



