During the course of the present year I reported a series of experiments on the hemolytic properties of extracts from organs and from tumors of dogs. I showed at that time that two sorts of hemolytic substances could be extracted from tumors. One of these, which was present in undegenerated tumors, was thermolabile, and hemolytic only when activated by a substance extracted from the red blood cells. This first substance is comparable to a similar hemolytic amboceptor present in certain normal organs, e. g., kidney. At about the same time and independently it was shown by Friedmann2 that a hemolytic substance could be extracted from the pancreas, which destroys the red blood cells of the same species, when complemented by some substance (probably of the lecithin group) present in the serum of certain other species. The second type of hemolysin is present only in necrotic tumors;