Malaria is a chronic disease, not alone an infection of the blood stream characterized by chills and fever. Failure to comprehend or detect its insidious course and its strong tendency to relapse, even after months or years, accounts for the fact that it still ranks as one of the serious social and economic problems. Some authors1 have recognized the persistent and prolonged course of malaria; nearly all acknowledge it to be the most widespread and destructive of tropical diseases. Because in its chronic form it is generally disguised, the problem of control is doubly hard to master.
We are not concerned here with early "classic" forms of malaria. These conditions constitute the minority and are largely limited to well known regions; they offer little or no difficulty in diagnosis and are easily controlled, temporarily at least, by specific treatment. Moreover, in these early infections plasmodia can usually be demonstrated