INSECTS AS INTERMEDIATE HOSTS 



405 



without wearing veils and gloves. Thus they lived through the most 

 dangerous part of the year, from early in July until late in October, 

 and not one became sick, although many of their neighbors became 



FIG. 209. The malaria parasite 



The parasite attacks the red blood corpuscle of a human being, a, and when it has 

 destroyed the corpuscle, d, it breaks up into a large number of spores, e, which may enter 

 other corpuscles and start a new cycle. When blood containing the malaria organism,/", 

 gets into the stomach of a mosquito (Anopheles'), the protoplasm undergoes various 

 changes, g, /i, resulting in two sexual forms, *',/, which conjugate and produce a fertilized 

 egg, k. This works its way into the wall of the insect's stomach, /, and breaks up into a 

 large number of tiny bodies, m, which finally lodge in the insect's salivary glands, n 

 When the insect again stings a person, some of these bodies, o, get into the victim's 

 blood and find their way into the red corpuscles, a, and the cycle begins again. /, stomach 

 of infected mosquito, showing swellings produced by the parasite 



infected with malaria during the summer. At the same time some 

 mosquitoes were caught and allowed to suck blood from persons suf- 

 fering from the disease. These mosquitoes were placed in little cages 

 and shipped to England. Here two young men one of them the 



