Experiments were then made with gliadin and with peptones obtained from gelatine, from edestin, and from casein. Edestin and casein were also injected by themselves. In all cases the result was the same. When substances, that are out of harmony with the plasma, are introduced into the plasma or serum of a given animal, we always find developed a special power of decomposing bodies belonging to the protein series, especially protein itself and its peptones. A specific activity of the injected substrates could be traced only so far as that, after the injection of proteins and peptones, ferments appeared in the plasma which were able to chemically reduce the derivatives of this group, but not, for instance, fats or carbohydrates. Conversely, no splitting of protein could be traced after injections of fats, of carbohydrates, or of amino-acids. On the other hand, after injection of a particular protein, or of a particular peptone mixture derived from a definite protein, not only were the injected substances decomposed by the plasma, but the decomposition extended to the whole group of proteins and their nearest derivatives.
That the process actually depends upon the presence of ferments can be proved in two ways. In the first place the splitting of a particular peptone solution, by the plasma of suitably prepared animals, was compared with the action of extracted yeast
