LIEBIG 65 



ters obstacles at every step. For me, on the contrary, 

 these transformations present a common character, 

 namely, that of taking place, every one of them, in 

 the presence of an organic substance in the process of 

 decomposition. We start a lactic or butyric fermen- 

 tation by means of old cheese, or putrid meat. As for 

 the alcoholic fermentation, Colin showed in 1828, that 

 this could be provoked by means of many organic 

 nitrogenous substances, different from the yeast of 

 beer, provided that they are in process of decomposition. 

 It is these dead substances which form the ferment. 

 I do not forget the experiments of Thenard on the almost 

 constant production of yeast in juices when in fermen- 

 tation; I do not forget, furthermore, the conclusions 

 of Cagniard-Latour and Schwann confirmed by Quevenne, 

 Turpin, and Mitscherlich. But this yeast does not 

 embarrass me, it enters into my system. If you admit 

 that it lives, then you admit also that it dies. Now, 

 it is in dying that it acts, as a result of the decomposition 

 which it undergoes at this moment and of that Thenard 

 furnishes us the proof." 



That savant had seen, in fact, that by adding 20 parts 

 of yeast to 100 parts of cane-sugar in solution in water, 

 he obtained a rapid and regular fermentation, after 

 which the remaining yeast collected on a filter weighed 

 no more than 13.3 grams. Added to a fresh and equal 

 quantity of sugar, this residue produced a fermentation 

 more slowly than the first time, after which it was 

 reduced to 10 grams, and was incapable of producing 

 a new fermentation. What more fitting to demon- 

 strate that the yeast destroys itself and is consumed by 

 its own activity? The theory of Liebig finds a good 

 defense, therefore, from this point of view. As for the 

 undeniable multiplication of the yeast in the vat of the 

 brewery, in the manufacture of wine, especially of the 



