1102 PATHOGENIC PROTOZOA 



calopus), and its development is briefly as follows: The bird is 

 inoculated by the mosquito with spindle-shaped young forms known as 

 sporozoites. These possess the power of ameboid motion, and rapidly 

 penetrate into an erythrocyte, in which they grow quickly ; they con- 

 stantly move about inside the cell until nearly full grown, and are 

 during this stage called trophozoites. The substance of the ery- 

 throcyte is rapidly consumed by the parasite and a dark pigment, 

 melanin or hemozoin, is formed from the destroyed hemaglobin. The 

 mature parasite divides into many small forms called merozoites. and 

 these, when freed by the rupture of the degenerated erythrocyte, 

 escape into the blood plasma, and if not phagocyted, penetrate other 

 erythrocytes and repeat the asexual or schizogenous cycle. The pig- 



FlG. 148. MlDGUT OF CULEX MOSQUITO, COVERED WITH OoCYSTS OF PROTEOSOMA 



PRECOX. V, VASA MALPIGHII. (After Doflein and Ross. MacNeal, "Path- 

 ogenic Microorganisms," published by P. Blakiston's Son & Co.) 



ment and undivided portion (restkorper) of the cytoplasm of the 

 mother cell accumulate in the bone marrow, spleen and other viscera. 



MALARIA 



This is one of the most common and widespread of preventable 

 human diseases, and in some localities is the cause of a greater mor- 

 tality and morbidity than tuberculosis. It is caused by one or more 

 of the three forms of the malarial plasmodium. As a rule the infec- 

 tions are simple, yet in the tropics it is not uncommon to find two 

 or even three species of plasmodia in the same patient, and this 

 condition is called a mixed infection. 



History. The disease under various names, as chills and fever, 

 Roman fever, Chagres fever, has been known since the greatest 

 antiquity. The cause was not discovered until 1880, when Laveran, a 

 French military surgeon stationed in Algeria first saw the organism 

 and described it as the cause of malaria. He saw and described ;oo f 



