THEORETICAL CONSIDERATIONS 263 



is too well known to be reviewed here. A few of the more recent 

 contributions will be referred to, as they serve to bring clearly before 

 us some of the possible factors to be considered in discussing the stimu- 

 lation of the process of fermentation. 



Shortly after Buchner's fundamental discover}?^ of the glycolytic 

 zymase, he and Meisenheim.er ^^ announced that the process of fer- 

 mentation consists of a number of successive steps, the products of 

 which are, in order, glucose, some hypothetical intermediate product 

 and water, lactic acid, and CO2 and alcohol. The experiments of 

 Brown and Glendenning^^ led them to believe that, in the transforma- 

 tion of starch to sugar, the process of hydrolysis is preceded by a 

 combination of the hydrolyte with the enzyme, and that "this 

 compound is much more unstable and less able to withstand the 

 action of the active ions or dissociated molecules of the electrolyte 

 than the original cane sugar. . . . According to this view these 

 active ions are the true hydrolytes, not the enzyme itself, which 

 has only an intermediate action." The enzyme is regarded figure- 

 atively " as the vice which holds the sugar molecule in a position 

 favorable for the splitting agent to act." 



In 1906 Slator^^ stated that the velocity of fermentation of dex- 

 trose varies with the amount of yeast present,* and is independent of 

 the concentration of the dextrose. This latter fact is explained on 

 the assumption that a compound is formed between the enzyme and 

 the sugar, as Brown and Glendenning had previously suggested. 

 Slator^^ states that, in the fermentation of sucrose enough sugar is 

 almost instantaneously hydrolyzed for the fermentative reaction to 

 attain its maximum velocity at once. From previous work and his 

 own investigations he conceives that fermentation of dextrose by 

 yeast involves the following steps in order : 



1. Diffusion of sugar into the yeast cell. 



2. Combination of dextrose and enzyme. 



3. Decomposition of this compound, forming an intermediate 

 compound. 



4. Diffusion of the products from the cell out into the solution. 

 It is the third step, he says, which proceeds slowly, and whose 

 velocity governs the rate of fermentation. 



*This, says Slator ^^ (p. 130), confirms the work of O'SuUivan,^^ but the latter dis- 

 tinctly says that, "The rule laid down by Dumas^^and supported by Brown ^* (for 

 dextrose) holds good also for maltose," viz., that the time taken to ferment solutions 

 of dextrose and maltose varies with the amount of the sugar present. 



