568 TISSUE RESPIRATION 



problem of the reducing constituents of the tissues we may 

 next take up the question of the consumption of oxygen in 

 the blood. Although earlier recognized that blood which 

 has been standing for a long time becomes impoverished in 

 oxygen, it was shown by the studies of Eduard Pfliiger and 

 of Alexander Schmidt in the sixties that not inconsiderable 

 amounts of oxygen may disappear from the blood withdrawn 

 from a vein with coincident production of carbonic acid. 

 Then when the search was made for the reducing substances 

 which it was presumed must necessarily be particularly rich 

 in the blood in asphyxia it was quickly realized that only the 

 blood corpuscles, but not the serum of the asphyxia blood, 

 were capable of fixing oxygen, and that the lymph of asphyxi- 

 ated animals was also free from reducing substances. 32 

 More recently the question of oxygen consumption in the 

 blood has been systematically studied particularly by P. 

 Morawitz and his pupils. They confirm the view that even 

 in condition of extreme asphyxiation there is no transfer of 

 substances with affinity for oxygen from the tissues to the 

 blood stream, which would be at all capable of oxidation in 

 the mere presence of oxygen. The oxidation processes 

 which take place in the blood are obviously connected with 

 the blood cells. While the blood corpuscles of adult human 

 beings manifest only a minor oxygen consumption, the 

 erythrocytes of young individuals exhibit this feature to a 

 highly important degree. The blood platelets, too, seem to 

 have something to do with oxygen consumption. It is a very 

 striking point that the blood of rabbits rendered anaemic by 

 a subchronic phenylhydrazin poisoning should (in contrast 

 with normal blood) show m vitro a marked oxygen consump- 

 tion and carbonic acid formation. This was proved to be 

 independent of the serum and the leucocytes, and was due to 

 the numerous young erythrocytes in the blood; the con- 



83 Literature : N. Zuntz, Hermann's Handb. d. Physiol., J t ", 92, 1882. 



