340 



ANIMAL BIOLOGY 



ilarly attack other corpuscles and multiply until a very large 

 number of blood corpuscles are destroyed. And poisonous prod- 

 ucts of the life processes of the parasites provoke the chills and 

 fevers characteristic of the disease. (Fig. 223.) 



But the parasites must make their escape before the human 

 host successfully combats the toxic substances, kills the parasites 





Sporozoite entering 

 human red blood 

 corpuscle 



Transmission 

 by bite of 

 Mosquito 



Schizogony 



(rapid increase 



of animals 



in blood) 



Merozoites 



CYCLE IN MAN 



CYCLE IN MOSQUITO 



Sporozoites enter 

 salivary glands 



Oocyst ruptures, 

 releasing sporo- 

 zoites into 

 body cavity 



Oocyst with fully 

 developed sporozoites 



Gametocytes in blood 



Female 



Transmission 

 by bite of 



Mosquito 



Maturation 

 in stomach 

 of Mosquito 



Macrogamete 

 (Egg) 



Fertilization 

 in stomach 



Ookinete (Zygote) 

 penetrates epithelium 

 of stomach 



Oocyst 



in wall of stomach 



Oocyst developing sporozoites 



Fig. 223. — Life history of a Malarial Parasite, Plasmodium malariae. 



by taking quinine, or succumbs to them. The getaway is accom- 

 plished, if at all, by a Mosquito biting the host and taking with 

 the blood certain sexual stages of the parasite which can develop 

 in the cold-blooded insect. And now the Mosquito is the host. 

 In its stomach the sexual phase of the life history of the malarial 

 parasite takes place, fertilization occurs, and finally the numerous 

 products of the zygote work their way to the mouth parts of the 

 Mosquito, where they await an opportunity to enter the human 

 blood. 



