Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/133

 because the whole organ has become similarly disharmonious.

The fact that the animal organism replies to the invasion of disharmonious substances—which, either taking their origin from the metabolism of certain cells of its organs, or being normal constituents of the cells, pass directly into the blood plasma—by means of specifically directed ferments, is of the greatest importance to physiology as well as to pathology.

Up to the present we have only been able to distinguish three different proteolytic ferments, namely, pepsin, trypsin, and erepsin. In addition to these, we may perhaps reckon as proteolytic the ferments of rennet, and of fibrin. Strictly speaking, erepsin must be excluded, because it is principally directed against the products of decomposition of albumen. Our experience of the defensive ferments induces the supposition that trypsin, for instance, is not uniform in its nature. Of course, it may be possible that there are ferments which, just as a master-key can open various kinds of locks, are able to decompose very different substrates, when these belong to the same type of compound. But it is more likely that, in trypsin, ferments of different kinds are combined, and that in the blood the different components each act separately.

The defensive ferments are, as we have already