ACUTE MALARIAL INFECTIONS.-011T knowledge of the pathological changes in acute malarial infections is necessarily largely derived from a study of the con dition of the internal organs as found in the grave forms of mstivo-autumnal in fection, as cases of quart= and tertian infections rarely reach the post-mortem table.
Melanosis due to the accumulation of pigment derived from the hmmoglobin by the action of the parasites constitutes one of the most significant anatomical changes. The distribution of pigment in the various organs imparts to them a peculiar slaty-gray color, which is char acteristic. Neither the malarial pigment nor the malarial parasite is distributed in the various organs with any degree of regularity. Not only is this irregularity manifested in different cases of infection with the same variety of parasite, but it has already been pointed out that in in fection with the quartan parasite the peripheral blood appears to contain the organism in greatest number, while in tertian infection to a certain extent and in mstivo-autumnal infection to an al most exclusive extent the parasites are to be found in the blood-vessels of the in ternal organs. It thus becomes evident, not only that melanosis varies in differ ent cases, but that pathological changes dependent upon the presence of the para sites are also irregularly distributed. It is also to be remarked that this varying distrithition of the parasites in all prob ability has an important bearing npon the clinical manifestations.
Pigment is found to accumulate to a greater extent in the capillaries than in the blood-vessels of larger calibre, and the same is true of the pigment-laden parasites. Especially is the accumula tion marked where the blood-current is retarded by the lessening of the calibre of the blood-vessel at the point where the artery merges into the capillary. Melanosis, therefore, as well as para sitic congestion, may be looked for in the capillaries of the cerebral convolutions, the dura mater, the pulmonary alveoli, the intestinal villi, and the glonaernli the kidneys. Ordinarily, however, the blood-vessels of the spleen, liver, and brain show the greatest accumula tions.
Characteristic effects due to long-con tinued malarial poisoning are mainly ob served (Ally in the liver, spleen, and kid neys. These effects are of two kinds:
pigmentary and cirrhotic. In the former black and yellow pigment is found dis tributed through the organ, while in the latter the organ presents a thickening of its strorna and a growth of new con nective tissue; and in each organ' the pigmentary changes are mainly found in the less chronic, and the cirrhotic in the more chronic, cases. L. F. Childe (Indian Medico-Chir. Review, Feb., '96).
The Spleen.—The spleen is always en larged, although in varying degree. Its consistency is diminished, often to such an extent that the attempt to remove it results in rupture of its tense capsule and the escape of its diffluent pulp. The pulp is frequently the scat of a mclanosis varying in intensity from a dark-brown to almost a deep-black discoloration; it is sometimes evenly distributed over the entire organ and sometimes irregularly deposited. The cut surface is usually a dark-gray-brown or slaty color, and the unpigmented Malpighian corpuscles stand out prominently. The capsule is thin and easily torn. Microscopically, dilatation of the venous sinuses, often marked, is to be observed. The pulp contains enormous numbers of red blood corpuscles, which in greater part are found to be infected with parasites in all stages of development, while occasionally free parasites are to be found.
The presence of large numbers of phagocytes, particularly the large cells known as macrophages previously re ferred to, is a marked characteristic. While leucocytic phagocytes occur, the predominating variety is this large cell, which exists in very considerable num bers. The protoplasm of these cells is seen to contain pigment-granules, in clumps or rods, as well as parasites free or included within their corpuscular hosts. The parasites, which are in vari ous stages of development, often com plete their cycle of existence while thus contained within the macrophages, and the latter not infrequently show evi dences of necrosis; a probable result of the destructive effect of the parasite. The splenic veins, while containing phagocytes laden with pigment, contain comparatively few infected blood-cor puscles; with the latter, however, the capillaries are usually filled.