326 LOUIS PASTEUR 





circumstance that the cells of these fruits cause fermenta- 

 tion without multiplying, this comes under the kind of 

 activity which we have already distinguished by the ex- 

 pression continuous life in cells already formed. 



We will conclude this section with a few remarks on the 

 subject of equations of fermentations, which have been 

 suggested to us principally in attempts to explain the re- 

 sults derived from the fermentation of fruits immersed in 

 carbonic acid gas. 



Originally, when fermentations were put amongst the 

 class of decompositions by contact-action, it seemed prob- 

 able, and, in fact, was believed, that every fermentation 

 has its own well-defined equation which never varied. In 

 the present day, on the contrary, it must be borne in mind 

 that the equation of a fermentation varies essentially with 

 the conditions under which that fermentation is accom- 

 plished, and that a statement of this equation is a problem 

 no less complicated than that in the case of the nutrition of 

 a living being. To every fermentation may be assigned an 

 equation in a general sort of way, an equation, however, 

 which, in numerous points of detail, is liable to the thousand 

 variations connected with the phenomena of life. More- 

 over, there will be as many distinct fermentations brought 

 about by one ferment as there are fermentable substances 

 capable of supplying the carbon element of the food of 

 that same ferment, in the same way that the equation of 

 the nutrition of an animal will vary with the nature of the 

 food which it consumes. As regards fermentation pro- 

 ducing alcohol, which may be effected by several different 

 ferments, there will be as in the case of a given sugar, as 

 many general equations as there are ferments, whether they 

 be ferment-cells properly so called, or cells of the organs 

 of living beings functioning as ferments. In the same way 

 the equation of nutrition varies in the case of different 

 animals nourished on the same food. And it is from the 

 same reason that ordinary wort produces such a variety of 

 beers when treated with the numerous alcoholic ferments 

 which we have described. These remarks are applicable 

 to all ferments alike ; for instance, butyric ferment is capable 

 of producing a host of distinct fermentations, in conse- 





