Now it is quite customary to treat the fermentative agency in putrefaction as if it were wholly bacterial, and, indeed, the putrefactive group of bacteria are now known as saprophytes, or saprophytic bacteria, as distinct from morphologically similar, but physiologically dissimilar, forms known as parasitic or pathogenic bacteria.

It is indeed usually and justly admitted that B. termo is the exciting cause of fermentative putrefaction.  Cohn has in fact contended that it is the distinctive ferment of all putrefactions, and that it is to decomposing proteinaceous solutions what Torula cerevisiae is to the fermenting fluids containing sugar.

In a sense, this is no doubt strictly true:  it is impossible to find a decomposing proteinaceous solution, at any stage, without finding this form in vast abundance.

But it is well to remember that in nature putrefactive ferments must go on to an extent rarely imitated or followed in the laboratory.  As a rule, the pabulum in which the saprophytic organisms are provided and “cultured” is infusions, or extracts of meat carefully filtered, and, if vegetable matter is used, extracts of fruit, treated with equal care, and if needful neutralized, are used in a similar way.  To these may be added all the forms of gelatine, employed in films, masses and so forth.

But in following the process of destructive fermentation as it takes place in large masses of tissue, animal or vegetable, but far preferably the former, as they lie in water at a constant temperature of from 60 deg. to 65 deg.  F., it will be seen that the fermentative process is the work, not of one organism, nor, judging by the standard of our present knowledge, of one specified class of vegetative forms, but by organisms which, though related to each other, are in many respects greatly dissimilar, not only morphologically, but also embryologically, and even physiologically.

Moreover, although this is a matter that will want most thorough and efficient inquiry and research to understand properly its conditions, yet it is sufficiently manifest that these organisms succeed each other in a curious and even remarkable manner.  Each does a part in the work of fermentative destruction; each aids in splitting up into lower and lower compounds the elements of which the masses of degrading tissue are composed; while, apparently, each set in turn does by vital action, coupled with excretion, (1) take up the substances necessary for its own growth and multiplication; (2) carry on the fermentative process; and (3) so change the immediate pabulum as to give rise to conditions suitable for its immediate successor.  Now the point of special interest is that there is an apparent adaptation in the form, functions, mode of multiplication, and order of succession in these fermentative organisms, deserving study and fraught with instruction.

Let it be remembered that the aim of nature in this fermentative action is not the partial splitting of certain organic compounds, and their reconstruction in simpler conditions, but the ultimate setting free, by saprophytic action, of the elements locked up in great masses of organic tissue—­the sending back into nature of the only material of which future organic structures are to be composed.