FERMENTS AND FERMENTATION. 85 



amount of substance acted upon. This fact alone speaks 

 against any idea that fermentation is dependent upon a 

 quantitative chemical decomposition between catalyzer and 

 catalyzed substance that, in other words, we are dealing 

 with a stoichiometrical reaction. 



It is well to note that what has been said holds true only 

 when infinite time is allowed. For shorter periods which 

 vary with the nature of the catalyzer and the nature of the 

 substance or substances catalyzed the degree of fermentation 

 is clearly and often definitely a function of the concentration of 

 the ferment. We cannot here enter into a discussion of the 

 influence of the concentration of a ferment upon the velocity 

 of the fermentation. In general it can be said that only 

 within exceedingly narrow limits- of time and concentration, 

 both of the substances~iinder^oing catalysis- and the catalyzer, 

 is the rate of fermentation approximately directly propor- 

 tional to the concentration of the ferment. -In the majority 

 of instances the variation is very great, and an increase in the 

 concentration of the ferment is not followed by a correspond- 

 ing increase in the rate of the fermentation. Thus doubling 

 the concentration of a ferment in a certain reaction mixture 

 does not multiply the rate of the catalysis by two, but by less 

 than two. 



The reason why the rate of catalysis is not proportional 

 to the amount of ferment added is not yet entirely clear. 

 It seems to be dependent, in part at least, upon a decom- 

 position which the ferment itself suffers, in consequence of 

 which its concentration is steadily decreased. More potent 

 than this seems to be the accumulation of the products of 

 the fermentation. The opinion has been expressed that 

 the accumulation of the products of the catalyzed reaction 

 injures the ferment, but this view can no longer be held, 

 since we have learned that the activity of many enzymes 

 is reversible. For example, in the action of maltase on 

 maltose and the production of dextrose we might assume 



