380 ON THE LACTIC FERMENTATION 
particles, whether of the same body or of some other unstable compound present 
in the solution. For, according to this view, it by no means follows that the 
substance which is the main subject of a fermentation must be that on which 
the ferment primarily acts, or indeed, that it should contribute at all to the 
nutrition of the growing organism. Thus, so far as I am aware, it is, in the 
present state of our knowledge, an open question whether in the case of the 
lactic fermentation, as it occurs in milk, the Bacteriwm lactis may not derive 
its nourishment exclusively from the caseine, the decomposition of which may 
act catalytically upon the milk-sugar. In that case the old view of the caseine 
being the ferment would have so much of truth in it that, though not the primary 
fermenting agent, it would occupy the position of an intermediary between the 
organism and the material which undergoes fermentation. 
In the more typical fermentations, such as the alcoholic and the lactic, 
the most characteristic and striking phenomenon is the catalysis or breaking 
up of an organic substance into simpler compounds out of all proportion to 
what is required for the purposes of the nutrition of the fermentative organism : 
but it would surely be a great mistake to restrict the term fermentation to cases 
like these. The only safe ground for us to take is, I believe, to regard as 
fermentative all chemical changes brought about by growing organisms in 
the media which they inhabit, whether those changes correspond or not 
with the immediate necessities of the organism. Thus the mouldy smell 
produced by the growth of Penicillium glaucum in paste or preserve is proof of 
the formation of some volatile product at the expense of the material in which 
the fungus is growing. The chemical change thus indicated must, I conceive, 
be grouped with the true fermentations, whether the penicillium does or does 
not cause more organic particles to be decomposed than actually contribute 
to its nutrition. And in like manner I should regard putrefaction as a fer- 
mentation without reference to the question whether the amount of albumen 
decomposed is or is not more than is required for the growth of the putrefactive 
bacteria. It is nevertheless desirable to give some distinctive appellation to 
fermentations such as the alcoholic and the lactic, in which the breaking up of 
the fermentable material occurs out of all proportion to the requirements of the 
organism concerned ; and for such cases I would venture to suggest the designa- 
tion catalytic fermentations. For certain it is that catalysis, or breaking up of 
organic substances into simpler compounds, without loss or gain of atoms, does 
take place in those fermentations, whether in the manner above suggested or 
otherwise ;* so that the proposed term would express an ascertained truth, 
independently of any theory. 
* Liebig threw out the suggestion that the yeast plant may by its growth produce a material capable 
