238 



THE BIOLOGY OF DISEASE 



Then the parasite escapes into the plasma of the blood and 

 later enters a fresh corpuscle. 



180. Source of the Malarial Parasite. — The word malaria 

 means bad air, for it was formerly believed that foul air 

 caused the disease. When it was learned that a definite 

 animal was the cause both in man and in other animals, 

 the problem was to find how the parasite entered the bod}^ 



Figure 241. — Malarial Swamp. 

 An ideal place for mosquitoes to breed. ] 



It has been proved to the satisfaction of scientists that the 

 malarial protozoan is injected into the blood by a particular 

 kind of mosquito (Anopheles) which carries malaria germs 

 in its body. 



The mosquito sucks the blood from a man or an animal 

 suffering from malaria. This blood contains some of the 

 malarial parasites, which pass into the stomach of the mos- 

 quito. They then migrate into the salivary glands of the 

 mosquito, so that as soon as the mosquito bites another 

 man or animal, it pours out some saliva which intro- 

 duces the parasites into the victim's blood. While in the 



