One of the most pleasing results of insulin therapy in some of the diabetic patients is the change from a morose to a cheerful frame of mind. This new cheerfulness may be induced by the good prognosis which is given to the patient who cooperates in a program of dietetic and insulin control. Aside from this, however, there is evident a marked, prompt change in some patients with the more severe cases of diabetes when treatment with insulin stops the loss of sugar and causes the metabolic processes to run once more in normal channels. This change led Cowie, Parsons and Raphael1 to a study of the sugar tolerance in the two phases of manic-depressive psychoses. They reported that the sugar tolerance is reduced in the depressive phase, and that it is changed toward the normal by the administration of insulin. Whether this will be of use in the