THEORY OF FERMENTATION 305 



that we have drawn from the preceding experiments, and 

 combats the explanation which we have given of the phe- 

 nomena of fermentation.* It is an easy matter to show 

 the weak point of M. Schiitzenberger's reasoning. We 

 determined the power of the ferment by the relation of 

 the weight of sugar decomposed to the weight of the 

 yeast produced. M. Schiitzenberger asserts that in doing 

 this we lay down a doubtful hypothesis, and he thinks that 

 this power, which he terms fermentative energy, may be 

 estimated more correctly by the quantity of sugar decom- 

 posed by the unit-weight of yeast in unit-time; moreover, 

 since our experiments show that yeast is very vigorous 

 when it has a sufficient supply of oxygen, and that, in such 

 a case, it can decompose much sugar in a little time, M. 

 Schiitzenberger concludes that it must then have great 

 power as a ferment, even greater than when it performs 

 its functions without the aid of air, since under this con- 

 dition it decomposes sugar very slowly. In short, he is 

 disposed to draw from our observations the very opposite 

 conclusion to that which we arrived at. 



M. Schiitzenberger has failed to notice that the power 

 of a ferment is independent of the time during which it 

 performs its functions. We placed a trace of yeast in 

 one litre of saccharine wort; it propagated, and all the 

 sugar was decomposed. Now, whether the chemical ac- 

 tion involved in this decomposition of sugar had required 

 for its completion one day, or one month, or one year, 

 such a factor was of no more importance in this matter 

 than the mechanical labour required to raise a ton of 

 materials from the ground to the top of a house would 

 be affected by the fact that it had taken twelve hours 

 instead of one. The notion of time has nothing to do 

 with the definition of work. M. Schiitzenberger has not 

 perceived that in introducing the consideration of time 

 into the definition of the power of a ferment, he must 

 introduce at the same time, that of the vital activity of 

 the cells which is independent of their character as a 

 ferment Apart from the consideration of the relation ex- 



International Science Series, vol. xx, pp. 179-182. London, 1876.* 

 D. C. R. 



