Plasmodia utilize the hemoglobin in the red blood cells of the host and a fine, granular, yellow-brown pigment is formed which ultimately localizes in the reticuloendothelial cells. The composition of this pigment has been a subject of discussion from the time the parasite was discovered. This pigment does not give the reactions for iron. Since it resembles melanin many have considered it as melanin. Brown in 1911 concluded from extensive chemical studies that this pigment was identical with hematin. Many investigators have confirmed this observation-•••. Apparently at this time it is generally accepted that the pigment produced by the malarial parasites is ferrihemate (hematin). The distribution of the hematin within the body of the host has been described frequently . I t is found primarily in the spleen, liver, and bone marrow. Taliaferro and Cannon noted that the number and the size of the granules of pigment vary copsiderably during the different stages of the In the acute phase the pigment usually occurs in small, more or less discrete granules, during the later phase of an acute infection and also during an infection of long standing the pigment occurs in clumps in masses. The pigment when extracted from the circulatory blood in P. knowlesi infections contains nonionized iron. This pigment is not liberated in soluble form from the parasites into the circulation in significant amounts according to Morrison and Anderson. Furthermore, these investigators observed in their study of the urine from monkeys infected with P. knowlesi that, 'urobilinogen, bile pigment, and ether-soluble porphyrins varied from negative to traces and could not be related to the course or extent of infection. In view of these observations the mechanism by which malarial pigment is eliminated from the host becomes significant. Two distinct types of pigment have been described in the liver in malaria, hemosiderin resulting from the destruction of erythrocytes and hematin formed by the parasites''. The former gives a positive reaction for iron with potassium ferrocvanide while the latter gives a negative reaction. McCallum also observed two types of pigment in phagocytic cells in his study of avian malaria. In a recent histologic study of the pigment occurring in the acute phase of an infection with P. lophurae in ducks it was observed that the potassium ferrocyanide staining for iron was negative. It is im-