ON THE NATURE OF FERMENTATION 351 
the sake of argument, that the lactic-acid ferment consisted of particles of some 
non-living substance, capable of self-multiplication as rapidly as the bacterium, 
but not living; a strange hypothesis, no doubt—but suppose we assume it. 
Suppose we admit that the true lactic ferment and the Bacterium lactis were 
merely accidental concomitants of each other, it would be absolutely incon- 
ceivable that these two accidentally associated things should be present in 
exactly the same numbers. And yet, according to the hypothesis, such would 
be only another mode of stating our observed fact, which amounts to this, that 
wherever there was a fermentative particle there was a bacterium, and wherever 
there was a bacterium there was a fermentative particle. But, suppose you 
admitted that—that there were exactly as many of the Bacterium lactis as there 
were of the hypothetical true fermentative particles—suppose you admitted that 
inconceivable thing, I say it would be again inconceivable that, if mutually 
independent, they should accompany one another in pairs, that invariably 
where there was Bacterium lactis there should be a ferment particle, and 
where there was no Bacterium lactis no ferment particle. That would be a 
thing as inconceivable as the other. Therefore, we have two inconceivables, 
one of which would have been sufficient to show that we cannot admit any 
other hypothesis than that Bacterium lactis is the cause of the lactic-acid 
fermentation. | 
But the experiment tends to even more than this. Where we find the 
effect so exactly proportioned, as regards the number of glasses affected with 
fermentation, to the adult bacteria that we count, we are led to infer that this 
particular bacterium, at all events, has not any spores—that there are no spores 
existing in addition to the bacteria. People seem often to assume that bacteria 
must necessarily have spores or germs. It seems to me an unlikely thing that 
they should. They are, as it were, a generative apparatus fer se, they are 
constantly multiplying; why should they have spores? I do not say that 
bacteria may not have spores. There are very different kinds of bacteria ; 
some may have spores, and some may not; but this sort of result seems to 
indicate that this particular bacterium has no spores ; at least, in the condition 
in which it exists in souring milk ; because, if we had, besides the bacteria that 
we can count, spores of bacteria disseminated through the liquid also, we should 
have the effect more than in proportion to the bacteria that we have counted. 
The only fallacy here is that it may be that the bacterium has not been diffused 
uniformly through the milk. Therefore, I do not say that in this case it is 
absolutely proved. But, at all events, this experiment gives us a line of inquiry, 
by means of which we may probably settle that point with regard to any 
individual case of bacterium. This, however, is a point I do not desire now to 
