CONSUMPTION OF OXYGEN. 477 



To how great an extent this takes place it is impossible to 

 say ; but it is evident, even from a study of the methods of 

 analyses of the blood for gases, that the property of absorbing 

 oxygen and giving off carbonic acid, which Spallanzani dem- 

 onstrated to belong to the tissues, is possessed as well by the 

 red corpuscles. Daring life it is not possible to determine 

 how far this takes place in the blood, and how far in the 

 tissues. Lagrange and Hassenfratz 1 advanced the theory 

 that all the respiratory change takes place in the blood as it 

 circulates ; but the avidity of the tissues for oxygen, and the 

 readiness with which they exhale carbonic acid, leave no 

 room for doubt that much of this change is effected in their 

 substance. The late experiments of Bernard, 3 showing that 

 when blood is sent to the glands in large quantities, the 

 oxygen is only imperfectly destroyed, the blood which is 

 returned by the veins having nearly the color of arterial 

 blood, are positive evidence against this view. 



Oxygen, carried by the blood to the tissues, is appropri- 

 ated and consumed in their substance, together with the nu- 

 tritive materials with which the circulating fluid is charged. 

 We are acquainted with some of the laws which regulate its 

 consumption, but have not been able to follow it out and as- 

 certain the exact nature of the changes which take place. 

 Some have said that oxygen unites with the iron of the 

 blood, or with the coloring matter of the corpuscles ; but ex- 

 periments on this point are contradictory and unsatisfactory. 

 Some have said that it unites with the hydro-carbons of the 

 blood and of the tissues ; but there is more evidence that it 

 enters into combination chiefly with the organic nitrogenized 

 principles. All that we can say definitely on this point is, 



1 HASSENFRATZ, Memoire sur la Combinaison de I 1 Oxygene avcc le Carbone et 

 V Hydrogene du Sang, sur la Dissolution de V Oxgyene dans le Sang, et sur la Maniere 

 dont le Calorique se degage. Annales de Chimie, 1791, tome ix., p. 261. 



2 Liquidcs de P Organisme, tome i. ; and unpublished lectures at the College of 

 France, 1861. In the latter, Bernard gives comparative analyses of the venous 

 blood from the submaxillary gland, showing a larger proportion of oxygen during 

 its functional activity than during repose. 



