340 ON THE NATURE OF FERMENTATION 
amygdalin, pointed out, and showed by irrefragable evidence, that the emulsin 
does not undergo any multiplication ; not only so, but that, after a while, the 
emulsin loses the property of acting on the amygdalin: but, for a considerable 
time, it continues to act upon it without undergoing apparently either increase 
or diminution of its bulk. It may be called a resolvent, the amygdalin being 
the resolved material. 
There are other cases equally striking that might be mentioned, not only 
in the chemistry of vegetables, but in the chemistry of our own bodies. There 
exists, for instance, in the saliva a material called ptyalin, which has a remarkable 
power of acting upon starch, so as to convert it into soluble compounds. In the 
gastric juice there is a material called pepsin, which has an equally remarkable 
property of acting on albuminous materials, fitting them for solution in digestion. 
3ut here again we find, when we come to consider the matter, that there is no 
evidence whatever that either pepsin or ptyalin is capable of self-multiplication. 
Each is secreted for the purpose and in the quantity in which it is required, 
but it has no faculty of self-propagation ; and I believe, if you search through 
the whole range of organic chemistry, you will not find a single established 
instance where any ferment, so called, destitute of life has been proved to have 
the power of self-multiplication. At the same time, gentlemen, it may be 
admitted that the thing might be theoretically possible. It 1s conceivable, for 
instance, that a resolvent, if we may so speak, of comparatively simple con- 
stitution might, by its action upon a resolvable compound, resolve it into sub- 
stances, one of which should itself be the resolvent, and, if that were so, the 
process might go on ad infinitum. That is conceivable; and accordingly, 
although we have no instance of the kind on record, yet we have persons in 
high authority, as teachers both of physiology and of pathology, maintaining 
the view that in putrefactive fermentation, for instance, the bacteria are pro- 
bably mere accidental concomitants ; that the real essential agent in the putre- 
faction is not an organism at all, but some so-called chemical ferment destitute 
of life. Andso long as we have authorities maintaining such a view, it 1s neces- 
sary to test its truth or falsehood by searching inquiry ; and such has been 
the object with which my investigations of the last two months have been 
conducted. 
As regards the putrefactive fermentation, we have already evidence in 
the flask and in the glass that I have shown you (the flask also has no putre- 
factive odour emanating from it), that blood has in itself no inherent tendency 
to putrefy. It must receive something from without, and that something is 
not mere oxygen or any other atmospheric gas. I have now to point out to 
you that the addition of water is not of itself sufficient to induce this fermenta- 
