FERMENTATION. 59 



of animal substances by the presence of animalculae,' 

 he wrote, ' reason very much like a child who would 

 explain the rapidity of the Ehine by attributing it 

 to the violent motions imparted to it in the direc- 

 tion of Bingen by the numerous wheels of the mills 

 of Mayence. Is it possible to consider plants and 

 animals as the causes of the destruction of other 

 organisms when their own elements are condemned to 

 undergo the same decompositions as the creatures 

 which have preceded them ? If the fungus is the 

 cause of the destruction of the oak, if the microscopic 

 animalcula is the cause of the putrefaction of the 

 dead elephant, I would ask in my turn what is the 

 cause which determines the putrefaction of the fungus 

 or of the microscopic animalcula when life is with- 

 drawn from these two organisms ? ' 



Thirty-two years later, and after Pasteur had 

 accumulated, during more than twenty years, proof 

 upon proof that the theory of Liebig would not stand 

 examination, a physician of Paris, M. Bouillaud, asked, 

 with the insistent voice of a querulous octogenarian : 

 ' Let M. Pasteur then tell us here, in presence of the 

 Academie de Medecine, w r hat are the ferments of the 

 ferments.' 



Before replying to this argument, which Liebig 

 and M. Bouillaud believed to be irrefutable, Pasteur, 

 wishing to mark all the phases of the phenomena, 

 expounded in a short preamble the part played by 



