ANALYSIS OF THE BLOOD FOE GASES. 459 



objection is fatal. It is necessary to wait until the froth 

 has subsided before attempting to make an accurate estimate 

 of the volume of gas given off. The following observation 

 of Magnus illustrates this fact. The observation was on the 

 human blood six hours after it had been thoroughly mixed 

 with hydrogen : 1 



Mood of Man. Carbonic acid. 



4*077 cubic inches. 1-013 cubic inches. 



3-650 " 0-781 " 



3-838 " 1-355 " 



After twenty-four hours, at the end of which time the 

 blood had no odor : 



4-077 cubic inches. 1-517 cubic inches. 



3-650 " 1-456 " 



3-833 " 2-075 " 



The excess of carbonic acid found twenty-four hours after, 

 over the quantity found six hours after, in the first and third 

 specimens, is a little over 50 per cent. ; while in the second 

 specimen it is very nearly 100 per cent. 



In these analyses the proportion of oxygen is not given. 

 The question naturally arises as to the source of the carbonic 

 acid which was evolved during the last eighteen hours of the 

 observation. This is evident, when we consider one of the 

 important properties of the blood. A number of years ago, 

 Spallanzani demonstrated that, in common with other parts 

 of the body, fresh blood removed from the body has, of itself, 

 the property of consuming oxygen ; and W. F. Edwards has 

 shown that the blood will exhale carbonic acid. In 1856, 

 Harley, by a series of ingenious experiments, found that 

 blood, kept in contact with air in a closed vessel for twenty- 

 four hours, consumed oxygen and gave off carbonic acid. 2 



1 G. MAGNUS, Sur les Gas que contient le Sang : Oxygene, Azote et Acide Car- 

 bonique. Annales de Chimie et de Physique, 2me serie, tome Ixv., 1837, p. 174. 



2 G. HARLEY, TJie Chemistry of Respiration. The British and Foreign Med~ 

 ico-Chirurgical Review, July, 1856, p. 328. 



