ELECTROENCEPHALOGRAPHIC studies have become an almost routine procedure at the New England Deaconess Hospital in examining diabetic patients who have frequent insulin reactions or seizures in which hypoglycemia is considered a possible precipitating factor. Although the incidence of epilepsy among diabetic patients has not proved to be greater than that in unselected persons of corresponding age groups, the occurrence of repeated insulin reactions in a specific case always raises the question whether they are due to an abnormally rapid change in the blood sugar or to instability of the nervous mechanism — that is, to an epileptoid tendency. The electroencephalogram . . .