SINCE 1949, when lithium salts were first utilized in the treatment of manic-depressive psychosis, there has been an enlarging body of evidence leading to the conclusion that they are highly effective and specific agents in the treatment of manic and hypomanic states, and in the prophylaxis of manic and depressive states.1-8Unlike the phenothiazines, they are believed to control the mood state at plasma levels which do not cause general sedation, and which have virtually no subjective effects in normal subjects.9This high degree of specificity suggests that lithium salts may prove to be important pharmacological tools for the study of the pathophysiology of manic-depressive disorders. In embarking on studies of the mechanism of action of the lithium salts, it seemed important to attempt to confirm the interesting reports of Trautner et al10that acutely manic patients retain more lithium ion than normal