MOSQUITOES 77 



blood corpuscles. Since that time the work has been 

 duplicated and verified by many reliable scientific workers 

 here and in Europe. So that now we know malaria is 

 caused by a very minute animal parasite living in the red 

 cells of the blood and destroying them by the millions. 

 The life history of the parasite has been carefully traced 

 in the blood of man and in the body of the mosquito. 



History of the parasite in man. — We will suppose 

 that one of these tiny parasites (sporozoit) has found its 

 way into a person's blood from the bite of a malarial 

 mosquito. If conditions are favorable, it soon goes inside 

 of a red blood cell, where it lives and grows, gradually 

 destroying the contents of the red corpuscle, and finally 

 taking up much of the space inside the cell. Finally, 

 the parasite (now called a schizont) inside the blood cell 

 has grown all it will, and it then divides into several 

 distinct individuals {merozoits) commonly called spores. 



The wall of the red blood corpuscle then bursts and these 

 parasites are set free in the liquid part of the blood. 

 Now if a person has a severe case of malaria, there may be 

 several millions of these parasites in the blood, each one 

 in its own red blood cell. Moreover, all the parasites 

 become mature, form spores, and burst out of these red 

 cells at just about the same time. It is just at the time 

 that the multitudes of minute parasites burst forth into 

 the liquid part of the blood that the chills and rigors be- 

 gin. There are at least three kinds of malarial parasites : 

 (1) the parasite that forms spores and causes chills every 

 two days, thus producing tertian fever; (2) the parasite 

 that forms spores and causes chills every three days, thus 

 producing quartan fever; (3) the parasite that causes 

 malignant fever which frequently becomes very serious. 



