264 THEORETICAL CONSIDERATIONS 



With reference to the stimulation of fermentation Dumas ^^ stated 

 in 1874, ^^^t ^^^ ^^^^ ^^ more gradual in darkness and in a vacuum, 

 and could be accelerated or retarded or destroyed by acids, bases and 

 salts. Acceleration, he said, is very rare. In 1875 Becquerel ^^ an- 

 nounced that fermentation was not retarded by the voltaic current 

 " as Gay-Lussac observed." Schulz and Biernacki are said by 

 Slator to have stated that very dilute solutions of poisons accelerate 

 the process, while large doses have the opposite effect (e. g., mercuric 

 chloride, iodine, potassium iodide). Slator ^^ was unable, under the 

 conditions of his experiments, to secure this acceleration by any such 

 reagents, and thinks that the effect previously interpreted as accelera- 

 tion of alcoholic fermentation is due to an acceleration of the growth 

 of the yeast, or to some other reaction. "We have not yet suc- 

 ceeded," he says,* "in finding a substance which will appreciably 

 accelerate fermentation by fresh living yeast." And later, f " The 

 velocity of such fermentation may be easily lessened by the addition 

 of certain inhibiting agents, but cannot be appreciably raised." 

 Among other conclusions, Slator-^ infers that, in the fermentation of 

 dextrose, laevulose, mannose, and galactose, " the enzyme combines 

 completely with the sugar, and that the velocity of formation of 

 carbon dioxide is determined by the rate of decomposition of this 

 compound. "$ 



At least three enzymes produced by yeast are to be considered ; 

 maltose and invertase, early recognized, and amygdalase, discovered 

 by Caldwell and Courtauld'' in 1907. Early in the" present year 

 (1908) we learn from the investigations of Trillat^®- ^'' and of Kayser 

 and Demalon^" that acetic aldehyde is a normal product of alcoholic 

 fermentation resulting from a further oxidation of the alcohol by the 

 living yeast cells that exist aerobically near the surface of the fer- 

 menting mixture. 



The above brief survey of the literature only emphasizes how im- 

 possible it is now, and how difficult it will be in the future to explain 

 the acceleration by radium rays of the evolution of gas in alcoholic 

 fermentation. Referring to the four steps hypothecated by Slator, 

 it may be that the radium rays increase the ionization of the sugar 

 solution and thus its rate of diffusion into the yeast cell ; or the 

 velocity of the reactions in the second and third steps ; or the rate of 



* Loc. cit., p. 234. 



tLoc. cit., p. 23S. 



5: Loc. cit,, p. 241. 



