The actual nature of immunizing and antitoxic substances is still somewhat open to question, and a recent research, a brief account of which is published in Science of March 10, is therefore of interest as throwing a possible side light on the problem. It appears that two investigators, Emmerich and Loew, have been engaged during the past year at Munich, in studying the relations of enzymes to infectious diseases. It had been suggested by Nencki and Pfeiffer, it appears, that the substances causing immunity and recovery might belong to the enzymes, and Pfeiffer believed that these enzymes were prepared by the animal and not by the bacteria themselves. De Schweinitz, however, has found an enzyme in the hog-cholera germ, immunizing guinea-pigs, but poisonous in a slightly higher dose, and now Emmerich and Loew claim to have found that certain bacteria, e.g., bacillus pyocyaneus, produce enzymes fatal to themselves and also