CHAPTER XXV 



MALARIA 

 Malaria is an infectious disease, the cause of which 

 is not a bacterium, but an animal micro-organism, a 'pro- 

 tozoon (plural ^protozoa). Its old name, ^'plasmodium 

 malarise," has been replaced by the term ''hemameba 

 malarise." This parasite was discovered in 1880 by 

 Laveran, a French army surgeon, and in the course 

 of work with the malarial parasite which followed upon 

 Laveran's discovery, Manson, Ross, Grassi, and others 

 found that the hemameba has two distinct life-cycles, 

 a sexual one, which takes place in mosquitos, and a 

 non-sexual cycle, occurring in the blood of human 

 patients. The young forms of hemameba, both male 

 and female, live in the Anopheles, a species of mosquito 

 which breeds and lives largely in stagnant pools and 

 marshes. In the stomach wall of this mosquito fer- 

 tilization occurs, and the development of the young 

 forms proceeds until, at the end of ten to fourteen days, 

 they are set free into the digestive tract of the mosquito 

 and pass, through the bite of the insect, into the blood- 

 stream of a human being. Here they penetrate the red 

 corpuscles, where they remain until they are fully 

 matured, and divide into a number of round or oval 

 segments, which are shed into the blood-stream. The 

 same cycle can be repeated indefinitely in man, the 

 stage of fever marking the setting free of amebulae. 



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