PLASMODIUM FALCIPARUM 249 



The various plasmodia are transmitted to man invariably by 

 the anopheles mosquito, in the bodies of which they undergo a 

 different (sexual) existence. It has been positively demonstrated 

 that the various plasmodia undergo an alteration of generations 

 and require two different hosts for their development, i.e., mos- 

 quito, man. 



The asexual development, or schizogony, takes place in the 

 blood of man, the sporogony, or sexual development, in the body 

 of the anopheles mosquitoes, the bite of which sets up an infec- 

 tion in man, since the sporozoites of the various plasmodia are 

 developed in the salivary glands of these mosquitoes. In the 

 act of biting, the sporozoites reach the erythrocytes where they 

 become the intracorpuscular hyaline bodies beginning again their 

 asexual cycle of development in the blood. 



That the mosquito is the intermediate host of the malarial para- 

 site and that the infection in man follows bites by infected mos- 

 quitoes has been abundantly proven. The mosquitoes that act 

 in this way are the various Anopheles; the Anopheles maculipennis 

 being the offender most frequently. The freshly formed schizonts 

 in the blood of an infected man are conveyed into the intestines 

 of the mosquito. Here sexual reproduction of the parasite begins. 

 The male elements, flagellar microgametes penetrate the female 

 elements, macrogametes (cellular), and after a time there appear 

 intra-cellular fusiform bodies, ookinets. These bore into the 

 intestinal walls of the mosquito and there remain. After a time 

 they are converted into round bodies, or ob'cysts. The nucleus 

 of the oocysts divides rapidly and other daughter nuclei are formed 

 and new cells called sporoblasts. After about eight days these 

 form the sporozoites. The number of sporozoites in each oocyst 

 varies from hundreds to many thousands (often 10,000). These 

 oocysts burst and the- sporozoites in the circulation find their 

 way to the salivary glands of the mosquito. When a mosquito 

 bites a human being they are introduced into the blood where 

 they are quickly transformed into the intracellular hyaline bodies 



