fusible stages (peptones). In the second case, we prepare the way for the ferments by producing peptones, which we then allow the ferments to decompose. So we allow serum of pregnancy to act upon a boiled placenta albumen, while in the optical method we use peptone produced from placenta albumen. In the first case, the appearance of diffusible stages of decomposition in the dialysate shows us that the decomposition has begun. In the second case, the change that takes place in the rotation enables us to infer a change in the composition of the added substrate, namely, of the peptone mixture.
Now very often, and probably in the great majority of cases, albumen itself does not pass into the circulation, but rather the products of its decomposition. We may easily understand that the optical method gives us trustworthv results, because it is quite possible that the peptone mixture used may also contain those stages of decomposition which have acted disharmoniously with the plasma. How, then, can we establish a decomposition of albumen? In those cases, for instance, where the cells of the body give off to the blood plasma peptones which still bear the characters of the cell, we start, in the dialysing process, at a higher stage of decomposition than was the case in the blood itself.
Unfortunately, we have no knowledge whatever concerning the nature of the ferments. We realize
