The advantages in cultivation of exoerythrocytic stages of malaria are fairly obvious. In the first place these stages represent a different portion of the life cycle which can be better understood through methods which permit observation and photography over extended periods of time. Since the exoerythrocytic stages live in cells which may be cultivated for long periods of time—perhaps indefinitely—they offer greater opportunities for certain types of study than the erythrocytic stages which live in cells incapable of reproduction. At the present time methods for separating exoerythrocytic stages from their host cells comparable to those used for erythrocytic stages by Trager have not been worked out. Therefore, the latter methods still present the only approach to the study of the physiology of the extracellular parasite.
Naval Medical Research Institute, National Naval Medical Center, Bethesda, Maryland.