238 THE INCOME OF ENERGY 



Hoppe-Seyler's Theory. 1 Living tissues consist of 

 easily combustible reducing substances, which split 

 the oxygen molecules, taking to themselves one atom 

 of and setting the other free in active state to 

 unite with any oxidizable substance present. 



Traube's Theory? In living protoplasm oxygen is 

 rendered active by an oxidizing ferment, which brings 

 the oxygen to bodies ordinarily oxidizable only by such 

 powerful agents as heat and strong alkalies. 



Inorganic bodies, e. g. platinum black, the oxides of 

 copper, silver, mercury, and vanadium, and certain iron 

 salts similarly act as oxygen carriers. Thus 



(1) Pt -i- 2 + H 2 = PtO + H 2 



(2) PtO + H 2 = Pt + H 2 



The oxygen carrier reduces H 2 2 , takes one atom 

 to itself, then gives off this atom in an active or 

 nascent state to oxidize any oxidizable compound 

 present ; e. g. guiac. Grape sugar takes from 

 indigo-blue, producing thereby indigo-white. The 

 indigo-white oxidizes itself to indigo-blue, then gives 

 up another atom of 0, and so on. 



ALCOHOLIC FERMENTATION 

 The Yeast Plant. Observe a solution of sugar 

 undergoing alcoholic fermentation. 3 Note the 

 bubbles of gas, the scum, the sour odor. 



1 Hoppe-Seyler: Zeitschrift fur physiologische Chemie, 1879, 

 ii, p. 1. 



2 Traube : Berichte der deutschen chemischen Gesellschaft, 

 1883, xvi, pp. 123, 1201, and earlier papers in volumes x and xv. 



8 The fermentation is assisted by providing the yeast plant 



