It is well known that when blood is removed aseptically from the body and kept at body temperature, the blood sugar steadily diminishes and may entirely disappear in twenty-four hours. This process is called glycolysis, and is thought to be caused by a ferment known as the glycolytic ferment. It is important to emphasize that this action occurs in vitro. Very little is known about this ferment, even less than the little we know of the fundamental nature of most of the other ferments. It has been demonstrated1that the glycolytic ferment is present only in the cellular elements of the blood, and not in the plasma; also there is evidence that the leukocytes contain considerably more than do the red blood cells. A ferment similar to, and in all probability identical with, the glycolytic ferment of blood is present in other tissues, perhaps in varying amounts in all