THE BIOCHEMISTRY OF RESPIRATION 



By H. M. VERNON, M.A., M.D. 



An article upon the " Mechanism of Tissue Respiration " was 

 published in this journal 1 by the writer some seven years ago, 

 but so great has been the advance in our knowledge of the 

 subject in recent years that it seems worth while to write a 

 second article, dealing chiefly with the fresh research which 

 has appeared in the interval. 



And, firstly, it should be pointed out that the clearer insight 

 which we now seem to possess into the fundamental chemical 

 processes which underlie the internal respiration of the tissues 

 is due to the gradually increasing recognition of the hypothesis — 

 first suggested by Hoppe-Seyler 2 in 1876 — that in all organisms 

 respiration is primarily anaerobic. Detmer 3 put it more clearly 

 by stating that all vital processes consist in a breakdown of 

 labile compounds, the decomposition products of which subse- 

 quently undergo oxidation. But these views were not generally 

 accepted, as it was evident that in the great majority of 

 organisms oxidation processes are of much greater importance 

 in the production of energy than hydrolytic or other changes 

 taking place in the absence of oxygen, and that in all but a 

 few of the lowest forms of life, such as certain bacteria and 

 parasites, oxygen is essential for the continuance of life. The 

 fact that carbon dioxide continues to be discharged for minutes 

 or even hours by frogs, snails, and other animals kept in an 

 oxygen-free atmosphere was attributed by Engelmann, Pfliiger, 

 Verworn, and others to the existence of a store of intramolecular 

 oxygen bound up in the tissues. Winterstein 4 pointed out that 

 this hypothesis has no solid experimental evidence to support 

 it, and there is no doubt that much of the supposed evidence is 

 better explained in other ways ; but, as we shall see later on, 



1 Vernon, Science Progress, 2, N.S. p. 160, 1907. 



2 Hoppe-Seyler, Arch.f. d. ges. Physiol. 12, p. 1, 1876. 



3 Cf. Detmer, Jahrbuch.f. wiss. Bot. 12, p. 237, 1879. 



4 Winterstein, Zeit.f. allgem. Physiol. 6, p. 315, 1907. 



251 



