It was observed by Dunn, Sheehan & McLetchie [1943] that the urine of animals injected with alloxan contains a considerable amount of sugar. This phenomenon became the object of an extensive study by these and other investigators, whose results have been reviewed [Liebmann, 1944; Ingle, 1945; Chen, 1945]. A single injection of alloxan in rats, rabbits and other animals causes, to begin with, a transient but pronounced hypoglycaemia, followed in 12–48 hr. by more or less marked symptoms of diabetes, i.e. glycosuria, polyuria and high blood-sugar values. At the same time the β-cells of the islets of Langerhans, which are looked upon as centres for the production of insulin, are seen to degenerate. The transient attack of hypoglycaemia may be due to the release of the total amount of insulin stored in the pancreas, and this release, therefore, may be regarded as the primary effect of the injury caused by