From the use of insulin in the treatment of schizophrenia much has been learned about hypoglycæmia, but nevertheless the physiopathology of the subject remains obscure. The intricacies of the ætiology of hypoglycæmia are well illustrated by Martin and Hellmuth's (1) study of 404 patients uninfluenced by insulin. The blood sugar in the majority of these cases was found at some time to be below 70 mgrm. %, and only in about one-third was an organic basis ascertained. Only 9% had definite symptoms of hypoglycæmia, 71% were asymptomatic and 20% were suggestive. The blood-sugar levels at which symptoms occurred differed in different individuals. Those showing symptoms at comparatively high levels belonged mainly to a group described as “symptomatic functional hypoglycæmia “, and those showing symptoms at lower levels were mostly suffering from psychoneurotic disorders. Martin and Hellmuth consider that few of these cases should be diagnosed as suffering from “hyperinsulinism” as described by Seal Harris (2) and Ross and Josephs (3).