grade of decomposition. For further protection, the lymph, with all its complicated arrangements, is interposed between the circulation and the cells of the body. Here everything is tested afresh; and nothing is let loose into the circulation that has not been rendered harmonious with the blood and its plasma. For ourselves, we have scarcely any doubt that the lymph system plays an important part in metabolism, along the lines we have indicated. Sometimes substances are reduced and converted into harmonious material; sometimes products of a definite type are built up. The lymph is, as we have pointed out before, to be considered as a sort of buffer between the cells of the blood and those of the body; as a neutral zone, in which everything is assimilated as far as possible.
If these views are correct, it should be possible to trace such substances as are in harmony with the body, but not with the blood and its plasma, by looking for definite ferments. It is quite conceivable that, in certain diseases, the cells only partially effect the decomposition of the nutritive material and of the constituents of the body, and that, to a certain extent, materials that are harmonious only with the cells are handed on to the lymph. The lymph, as already pointed out, would in many cases do its best to correct this failure by means of its cells, the leuco-
