THE INFECTIOUS DISEASES. 285 



tissues of the body finally overcome the parasite, or treatment with qui- 

 nine destroys the merozoites by means of its toxic action ou these imma- 

 ture forms. 



THE LESIONS OF MALARIA. 



The characteristic lesions of acute malarial infection are found in the 

 blood, the liver, spleen, kidneys, and brain. 



The alterations in the blood are chiefly confined to the diminution in 

 number of the red corpuscles, due to their destruction by the parasites 

 developing in them and to a reduction in the haemoglobin content of 

 those which do not contain parasites. These changes are apparently due 

 to some toxic agent, for which there is additional evidence in the poly- 

 chromatophilia and granular degeneration of the body of the red cell so 

 often present in severe malarial infectious. The evidence of some poison 

 acting on the protoplasm of the red cell is found, not only in those cells 

 in which the organism is developing, but is more abundant in those cells 

 in which no plasmodia are present. 



The leucocytes show slight qualitative changes, there being usually 

 present a relative increase in the large mouonuclear cells. Pigmented 

 leucocytes are often seen, and in very severe infectious large inacrophages 

 loaded with pigment may be seen in the circulating blood. In severe 

 cases the pigment, which is derived from the haemoglobin of the blood 

 corpuscle and forms the granules in the body of the parasite, may be 

 found free in the general circulation, but is usually soon removed by 

 the leucocytes and the phagocytic cells of the liver, spleen, and bone 

 marrow. The brain in cases of pernicious aestivo-autumual fever is often 

 much congested, and the smaller capillaries may be filled with enormous 

 numbers of the plasmodia in various phases of development ; there may 

 also be small punctate haemorrhages in the w r hite matter. The deposition 

 of the malarial pigment in the cortex may give to the latter a dark red- 

 dish-brown color, or it may be almost black. The spinal cord shows 

 similar changes. 



The liver in acute cases may show focal necroses resembling those 

 present in other infectious diseases. The ejidothelium of the livei^capil- 

 laries may contain much pigment (see Fig. 359, p. 592), while thelumlna 

 of the Capillaries may be stuffed" with plasmodia in various stages of de- 

 velopment. The kidneys may show albuminous degeneration, and while 

 the intertubular capillaries may be filled with pigmented leucocytes 

 there is not, as a rule, a great accumulation of plasmodia in the vessels. 

 A moderate diffuse nepjirjtis. is occasionally seen. The capjllariespf the 

 mucosa of thlTstomocA and the intestines may be filled with parasites in 

 cases~with choleraic symptoms, and" there may be^i colasiderablelunouut 

 of necrosis in the epithelium of the mucosa of the intestines. The bone 

 marrow usually contanTs largo numbers of the plasmodia, chiefly seg- 

 menting forms. A good deal of pigmentation is present, and an active, 

 phagocytosis js carried on, mainly by the giant-cell inacrophages present 



