NATURE OF PROTOPLASMIC RESPIRATION. 335 



stance which unites readily with nascent hydrogen can replace 

 the atmospheric oxygen and permit oxidation to go on in the 

 absence of air. In the example just cited levulose acts in this 

 way. This principle is of considerable importance in bacteriology. 



The hypothesis just stated necessitates, as will be seen, a total 

 abandonment of the common interpretation of anaerobic respiration 

 as taking place at the expense of the oxygen of some food stuffs 

 and shows at a glance the identity of the process in aerobic and 

 anaerobic forms. 



What is the nature of the process going on in protoplasm by 

 which this decomposition of water is produced ? 



A great number of reactions occur of just this type in organic 

 and inorganic chemistry. One of the most striking is the oxida- 

 tion of alcohol to aldehyde accompanied by the reduction of 

 benzophenone to benzopinakon which occurs when an alcoholic 

 solution of benzophenone is exposed to sunlight. The interpre- 

 tation of this reaction as given by Nef's 1 brilliant hypothesis 

 gives at the same time an interpretation of the living respiration 

 which wonderfully simplifies the problem of the chemical basis 

 of life. 



According to Nef many organic reactions are brought about 

 by a change in valence of the carbon atom from four to two. In 

 the case just cited alcohol in the sunlight splits off water to some 

 degree just as it does when heated and forms extremely active 

 ethylidene particles as follows : 



I. CH 3 - CH 2 OH s-^ CH 3 CH = + H 2 O 



Ethylidene. 



If now benzophenone is present to act as a depolarizer the active 

 ethylidene attacks the water and oxidizes itself to aldehyde 

 setting free nascent hydrogen which reduces the benzophenone. 



II. 



Aldehyde. 



III. 2H + 2(C 6 H 5 ) 2 C -O = [(C 6 H 5 ) 2 CHOJ 2 



Benzopinakone. 



Y Y 



It will be seen how exactly this process fulfills the require- 

 ments of the facts for a complete theory of respiration. Owing, 



1 Nef, Liebig's Annalen, vol. 335, 1904, p. 192. 



