OXYGEN CONSUMPTION IN THE BLOOD 567 



To quote Heffter : 28 i ' The principal results of the above 

 investigations may be summarized by stating that the reduc- 

 tions of methyl ene blue, of sulphur, tellurium oxide, etc., by 

 animal and vegetable cells are not the effects of enzyme 

 action. 29 They are to be referred to the presence of proteid 

 substances which contain one or more sulphydril groups. 

 The readily detached hydrogen of this group may, as shown 

 by the behavior of cystein and similar compounds, exert 

 strong reducing action. It is also capable of directly uniting 

 with molecular oxygen. For this reason the sulphydril com- 

 pounds of the tissues are autoxidizable. Herein, at least in 

 part, may be seen an explanation of the affinity of the cells 

 for oxygen as well as of the possibility of formation of 

 hydrogen peroxide. " Certain tissue constituents may act 

 in this connection as catalyzators and accelerate the reduc- 

 tion brought about by the sulphydril groups. 



One would be going too far, however, to refer all reduc- 

 tions in the tissues to the influence of the sulphydril groups. 

 The reduction of nitrates and of nitrobenzol, for example, 

 seems to rest on a different basis. 30 Attention has been 

 called, especially by the investigations of S. Frankel and his 

 associates, 31 to the strong reducing action of unsaturated 

 tissue phosphatids. However, as we possess no basis at 

 the present time for holding that reductions of this kind are 

 actually concerned in the vital combustions it seems alto- 

 gether too early to attempt to base "A Theory of Tissue 

 Eespiration Through Intermediary Bodies " on this status. 



Oxygen Consumption in the Blood. As a sequel to the 



a A. Heffter, Med. Naturw. Arch., l t 103, 1907. 



'"Abelous, Iscoveso and others have likewise expressed doubt as to the 

 enzymic nature of the reductases. 



80 Cf. also A. Bach; Arch. Sc. nat. GenSve, 82, 27, 1911, cited in Centralbl. 

 f. d. ges. Biol., 1911, No. 2555; Biochem. Zeitschr., 31, 443, 1911. 



81 S. Frankel and A. Nogueira, Biochem. Zeitschr., 16, 378, 1909; S. Frankel 

 and L. Dimitz, ibid., 21, 337, and Wiener klin. Wochenschr., 1910, No. 61; 

 S. Frankel, Dynamische Biochemie, pp. 31-34, 1911. 



