Abstract
Summary 1. Untreated Plasmodium gallinaceum infection in chicks is an acute disease characterized by large numbers of pigment-producing parasites in erythrocytes and only a few non-pigmented parasites in reticulo-endothelial cells of the spleen, liver and intestine, and in the endothelial cells lining the blood vessels of the heart and lungs. 2. On the other hand, the disease in chicks receiving quinine in suppressive doses is chronic and is characterized by large numbers of non-pigmented schizonts in the reticulo-endothelial and the endothelial cells of all the organs examined and only rare parasitized erythrocytes. 3. It appears that the metabolic requirements of erythrocytic and exoerythrocytic parasites may be different because the two forms of the parasite may provoke varying reactions in the liver and because they respond differently to quinine therapy. The glycogen depletion in the liver cells in quinine-treated chicks may, however, be a function of the general toxicity of the disease rather than of the metabolic requirements of the exoerythrocytic parasites.