156 MALARIA 



process of asexual multiplication in the human blood corpuscles 

 begins over again. Since it takes ten or 12 days for the sexual 

 cycle to be completed in the case of sestivo-autumnal malaria, 

 an infected mosquito is not dangerous for at least this length of 

 time after biting a malarial patient. However, once the new 

 generation of spores has been developed, the mosquito remains 

 dangerous for several weeks and may infect many persons, as not 

 all the parasites are poured out of the salivary glands at one 

 biting. 



It is commonly believed that malaria parasites not only do not 

 develop but cannot live in the mosquito at winter temperatures, 

 and conflicting results have been obtained from experimentation. 

 King in America and Wenyon in Macedonia have succeeded in 

 exposing infected mosquitoes to low temperatures without destroy- 

 ing the parasites, whereas Mayne (Mitzmain) found that in 

 Anopheles infected prior to hibernation, healthy normal sporo- 

 zoites did not last through the winter in the salivary glands. Rou- 

 baud obtained similar results in France. It is still doubtful 

 whether the malaria parasites normally pass the winter in the 

 mosquito hosts in places where the mean temperature falls much 

 below 60 F. for any considerable time. 



Other Species. The other species of malarial parasites dif- 

 fer only in minor details of their structure and development. 

 The tertian parasite, Plasmodium vivax, during the early stages 

 of its development in the blood corpuscles is extremely active. 

 Its unceasing restless changing of shape is fascinating to watch 

 under the microscope and one feels that it was very appro- 

 priately named " vivax." Unlike the malignant parasites of 

 sestivo-autumnal malaria, the tertian parasites do not tend to 

 clump together, and so do not become plugged in the capillaries 

 but remain constantly in the circulation. To this fact, as will 

 be shown later, is due the " benign " nature of this and also of 

 the quartan parasite. The tertian parasites have the peculiarity 

 of growing very large and of causing the corpuscles which they 

 parasitize to enlarge and become unhealthy in appearance. 

 The number of spores which result from the sporulation every 

 48 hours ranges from ten to 25. According to Ross the normal 

 number of splits of the nucleus is four, which would result in 

 16 spores. One of the most striking points of difference from 

 the " malignant " parasites is the fact that the gametocytes 



