its physical characters, and of the circumstances in which it occurs, hæmozoin may with confidence be regarded as the specific product of the malaria parasite itself.
Source of the pigment in the pigmented leucocyte.——If further evidence be required of the identity of the intraparasitic pigment and that found in the tissues, it will be supplied by a study of the fate of the pigment grains and clumps set free in the blood on the breaking-up of the segmented parasite.
If malarial blood, drawn during the rigor and early stages of acute attacks, and even at other times, be examined, large mononuclear leucocytes carrying grains or even blocks of black pigment may be encountered. If the observer be fortunate and persevering he will sometimes actually see whence this pigment is derived; he may even detect the leucocytes in the act of taking it up. He may see the pigment set free in the liquor sanguinis by the falling to pieces of a segmenting parasite; and he may then see a phagocyte creep across the field of the microscope and slowly engulf the little block. This undoubtedly is a principal source of the pigment in the leucocytes. Other, though possibly less important, sources are the effete gametes and, especially in the large cells of the spleen, necrosed parasite containing red blood-corpuscles.
Phagocytosis in the spleen.—— The evidence of phagocytosis in the spleen in malaria is very remarkable. Not only are large and small masses of hærnozoin included in the macrophages, in the smaller cells, and in the endothelium, but entire blood- corpuscles, sometimes as many as eight or nine, mostly containing parasites, besides free parasites, free hǣmozoin, and fragmented hæmoglobin, are frequently to be seen in one and the same phagocyte. Sometimes one haemozoin-laden phagocyte may be seen included in another phagocyte, and these perhaps in a third.
Blood of the splenic vein and liver.—— Of all the vessels of the body the splenic vein is that in which malarial pigment is most abundant. Whereas in other vessels it is found to be included in ordinary leucocytes,
