438 



SPECIFIC MICRO-ORGANISMS 



a spherical cyst filled with an enormous number of thread-like 

 sporozoits. These escape into the body cavity of the mosquito 

 as the cyst bursts, and are generally distributed throughout the 

 body of the insect. They assemble, probably as a result of some 

 chemical stimulus, in the salivary glands of the mosquito, whence 

 they are injected into the wound as the insect bites, and at once 

 invade erythrocytes to begin the cycle of schizogony. 



The discovery of the sexual cycle of pro- 

 teosoma in the mosquito and the conclusive 

 proof that this form of bird malaria is trans- 

 mitted by a mosquito stands to the ever- 

 lasting credit of Ronald Ross. His brilliant 

 discovery made in India in 1898, pointed 

 the way to the solution of the whole problem 

 of the transmission of the malarial diseases 

 and their practical restriction. 



Proteosoma is a favorable parasite for 

 class study, as it is readily transmitted from 

 bird to bird (sparrows or canaries) by in- 

 jection of infected blood, and the parasites, 

 often become very numerous in the blood. 

 Oocyst of There seems to be no good reason for placing 

 this organism in a separate genus from the 

 human malarial parasites. 



Plasmodium Falciparum (Praecox).— 

 Laveran in 1880 discovered . the first ma- 

 larial parasite in the blood of man and correctly interpreted 

 bis observations. The distinctions between the three species 

 was recognized by Golgi, and the hfe history of the parasites 

 and especially their relation to mosquitoes and insects in gen- 

 eral has been most thoroughly studied by Grassi.^ PL falcip- 

 arum is the parasite of estivo-autumnal or pernicious malaria 

 of man. The young organism is i to 1.5/* in diameter. It pene- 

 trates a red blood cell and enlarges. A vacuole appears in the 

 1 Grassi: Die Malaria, lite Auflage, Jena, igoi. 



Fig. 198 

 Proteosoma prtBcox, de- 

 veloped on the intestine 

 of Aides (Stegomyia) ca- 

 lopus, showing numerous 

 sporozoits. (From Do- 

 Jlein ofler Neumann.) 



