356 LOUIS PASTEUR 



ferent if they had been gradually brought under the action 

 of air in small quantities at a time. 



We are compelled here to admit that vibrios frequently 

 abound in liquids exposed to the air, and that they appro- 

 priate the atmospheric oxygen, and could not withstand a 

 sudden removal from its influence. Must we, then, believe 

 that such vibrios are absolutely different from those of 

 butyric fermentations? It would, perhaps, be more natural 

 to admit that in the one case there is an adaptation to life 

 with air, and in the other case an adaptation to life with- 

 out air; each of the varieties perishing when suddenly trans- 

 ferred from its habitual condition to that of the other, whilst 

 by a series of progressive changes one might be modified 

 into the other. 10 We know that in the case of alcoholic 

 ferments, although these can actually live without air, prop- 

 agation is wonderfully assisted by the presence of minute 

 quantities of air; and certain experiments which we have 

 not yet published lead us to believe that, after having lived 

 without air, they cannot be suddenly exposed with impunity 

 to the influence of large quantities of oxygen. 



We must not forget, however, that aerobian torulae and 

 anaerobian ferments present an example of organisms ap- 

 parently identical, in which, however, we have not yet been 

 able to discover any ties of a common origin. Hence we are 

 forced to regard them as a distinct species ; and so it is pos- 

 sible that there may likewise be aerobian and anaerobian vib- 

 rios without any transformation of the one into the other. 



The question has been raised whether vibrios, especially 

 those which we have shown to be the ferment of butyric 

 and many other fermentations, are in their nature, animal 

 or vegetable. M. Ch. Robin attaches great importance to 

 the solution of this question, of which he speaks as fol- 

 lows:" "The determination of the nature, whether animal 

 or vegetable, of organisms, either as a whole or in respect to 

 their anatomical parts, assimilative or reproductive, is a 

 problem which has been capable of solution for a quarter 

 of a century. The method has been brought to a state 



10 These doubts might be easily removed by putting the matter to the 

 test of direct experiment. 



11 ROBIN, Sur la nature des fermentations, &c. (.Journal de I'Academie et 

 de la Physiologic, July and August, 1875, p. 386). 



