316 M. L. Pasteur on the Production of Fermentation 



in liquids freely exposed to the air^ provided the layer of fluid is 

 of sufficient thickness. It may under such circumstances be 

 shown that those Infusoria which consume oxygen gas multiply 

 at the surface ; whilst those are developed in the liquid strata 

 beneath which do not require this gas for their existence, and 

 these are at the same time preserved from its injurious contact 

 by the former class of beings. 



" In fine, there is no need to resort to any artificial measures 

 to deprive fluids of their oxygen gas. All the precautions I 

 adopted in my experiments for this purpose were wholly super- 

 fluous. The abstraction of the oxygen is naturally effected, as a 

 matter of course, before fermentation begins, in every instance 

 of spontaneous fermentation. 



" The nature of the experiments above detailed, and the com- 

 position of the materials employed in them, deserve particular 

 notice when we come to inquire what may be the primary cause 

 of the fermentation. I have referred to the prevalent theories 

 as requiring, as indispensable for the act of fermentation, the 

 concurrence of albuminoid matter and of a ferment. For my 

 part, I recognize their presence to be not absolutely necessary, 

 but useful, inasmuch as they supply a certain material for 

 the action of the ferment, which is itself an organized being 

 whose germ cannot develope or reproduce itself except in the 

 presence of nitrogen and phosphates. These are especially 

 the kind of suitable materials that the ferment obtains from the 

 presence of albuminoid substances. This theory is so true in its 

 application, that, as before seen, the azotized plastic matter may 

 be entirely dispensed with, and its place supplied by an ammo- 

 niacal salt mingled with alkaline and earthy phosphates. 



" But it further results from the composition of the fluid just 

 spoken of holding a tartrate in solution, that the sole carbona- 

 ceous material for fermentation is the tartaric acid, or the fer- 

 menting body itself. Hence this further result follows, that 

 at the least the animalcule derives in the first place all its 

 carbon from the fermentable matter. There is no question, if 

 preconceived notions relative to the cause of fermentation be 

 laid aside, that under the conditions which we have described, 

 the ferment obtains its nutrition at the expense of the fermenting 

 material, and that so long as the life of the infusory organism 

 lasts, so long does a transfer of matter go on from the ferment- 

 ing substance to that which provokes its transformation. The 

 hypothesis of a purely <;atalytic action, or of simple contact, 

 consequently cannot be admitted as true, any more than the 

 opinion, to be afterwards combated, that the nature of a fer- 

 ment is exclusively found in dead albuminoid matter. 



" It must be granted that the fact of the nutrition of the fer- 



