318 LOUIS PASTEUR 



characterize the life of all ordinary beings, animal or 

 vegetable, but by which the latter may be affected, more or 

 less, in a way which brings them, to some extent within 

 the class of ferments, properly so called. We can even 

 conceive that the fermentative character may belong to 

 every organized form, to every animal or vegetable cell, 

 on the sole condition that the chemico-vital acts of assimila- 

 tion and excretion must be capable of taking place in that 

 cell for a brief period, longer or shorter it may be, with- 

 out necessity for recourse to supplies of atmospheric oxygen ; 

 in other words, the cell must be able to derive its needful 

 heat from the decomposition of some body which yields a 

 surplus of heat in the process. 



As a consequence of these conclusions it should be an 

 easy matter to show, in the majority of living beings, the 

 manifestation of the phenomena of fermentation; for there 

 are, probably, none in which all chemical action entirely 

 disappears, upon the sudden cessation of life. One day, 

 when we were expressing these views in our laboratory, 

 in the presence of M. Dumas, who seemed inclined to admit 

 their truth, we added : " We should like to make a wager 

 that if we were to plunge a bunch of grapes into carbonic 

 acid gas, there would be immediately produced alcohol and 

 carbonic acid gas, in consequence of a renewed action 

 starting in the interior cells of the grapes, in such a 

 way that these cells would assume the functions of yeast 

 cells. We will make the experiment, and when you come 

 to-morrow it was our good fortune to have M. Dumas 

 working in our laboratory at that time we will give you 

 an account of the result." Our predictions were realized. 

 We then endeavoured to find, in the presence of M. Dumas, 

 who assisted us in our endeavour, cells of yeast in the 

 grapes; but it was quite impossible to discover any. 1 



l To determine the absence of cells of ferment in fruits that have been 

 immersed in carbonic acid gas, we must first of all carefully raise the 

 pellicle of the fruit, taking care that the subjacent parenchyma does not 

 touch the surface of the pellicle, since the organized corpuscles existing on 

 the exterior of the fruit might introduce an error into our miscroscopical 

 observations. Experiments on grapes have given us an explanation of a 

 fact generally known, the cause of which, however, had hitherto escaped our 

 knowledge. We all know that the taste and aroma of the vintage, that is, 

 of the grapes stripped from the bunches and thrown into tubs, where they 

 get soaked in the juice that issues from the wounded specimens, are very 

 different from the taste and aroma of an uninjured bunch. Now grapes 



