THE BLOOD AND ITS FUNCTIONS 



133 



the method by which these little parasites find their way into 

 the blood. They cannot pass directly from person to person 

 and hence the disease is not contagious. It used to be sup- 

 posed that malaria came from bad air, especially from the air 

 of swamps, night air being thought particularly dangerous. 



Surface of Water 



FIG. 71. MOSQUITOES 



Figures a and b show the larvae in water, a being the harmless species (Culex) and 

 b (Anopheles) the species that carries malaria. At c is shown the position assumed 

 by the harmless type upon alighting, and at d the position of the dangerous one. In 

 the latter it will be seen that the body and head are in one straight line while in the 

 harmless species the body is bent at the neck. At e is shown the dangerous Anophe- 

 les with spotted wings and five hair-like projections (or feelers) in front; at / the Cu- 

 lex with plain wings and three feelers. 



But these theories have been disproved. It has been found 

 that these parasites live in a certain kind of mosquito. If 



