784 PATHOGENIC PROTOZOA 



In conclusion, it may be affirmed that any district, no matter how 

 notorious, may be freed from malaria, if necessity demand it and 

 money be forthcoming, by means of the above measures. 



Pathology. The pathological features of the disease are quite defi- 

 nite; at autopsy there is evidence of some secondary anemia, due to 

 the destruction of enormous numbers of erythrocy tes ; the hemozoin, 

 in well-marked cases, accumulates in the viscera until they are choco- 

 late or slate colored ; the spleen is enlarged and friable, and the liver 

 and kidneys may show cloudy swelling. In smears prepared from the 

 spleen, liver, kidneys, brain and bone marrow, parasites and hemozoin 

 will be found, although the former may not be numerous. The distri- 

 bution of the parasites is usually unequal, but they are often present 

 in the spleen and brain in greatest numbers. 



The origin of the pigment has already been described; it is phago- 

 cyted and accumulates in the viscera, but after a time disappears in 

 some unknown way ; its presence, therefore, is an indication of ma- 

 laria in recent years. It must be distinguished from hemosiderin, a 

 yellowish pigment found in the viscera after extensive destruction of 

 red blood cells. Hemozoin is soluble in alkalis and insoluble in acids, 

 water, chloroform, alcohol and ether, while hemosiderin is insoluble in 

 acids and alkalis but soluble in alcohol. Both contain iron, yet the 

 former (hemozoin) does not give a Berlin blue reaction, while it is 

 present with the latter. 



The leucocytes, although increased during paroxysm, are soon 

 diminished so that leucopenia is characteristic of the disease ; in addi- 

 tion, there is a relative increase in the mononuclear leucocytes. The 

 loss of hemoglobin is very great, yet is quickly recovered from during 

 convalescence. 



In fatal cases of aestivo-autumnal fever a striking feature is the 

 presence of innumerable infected red cells in the capillaries of the 

 brain or abdominal viscera, A smear from a pigmented brain may 

 show a capillary thrombus made up of infected erythrocytes, most of 

 them showing the sporulating stage. In deaths after repeated ma- 

 larial attacks the kidneys will show, in addition to the presence of 

 many parasites, a marked chronic diffuse nephritis, one of the most 

 important sequelae of the disease. 



Immunity. The disease is strictly confined to human beings, as 

 none of the lower animals are susceptible; there appears to be some 

 racial and acquired immunity, although it is incomplete; in native 

 settlements the number of children showing parasites in the blood is 



