MALARIA 279 



It is now generally considered that the crescentic bodies 

 represent a sort of resting form for the life of the organism 

 outside the body. 



In the mosquito fed on crescent containing blood, crescent 

 bodies are found plentifully. On spreading a drop of this 

 blood from the mosquito on a slide, and observing without 

 staining, it will be found that in five minutes or so one-third 

 of the crescents become spherical, and a short time afterwards 

 about 5 per cent, of the spheres are seen to develop flagella. 



According to Surgeon-Major Ross, it may be taken as 

 established that Dr. Manson's theory is substantially correct 

 respecting the part played by the mosquito as host to the 

 parasite ; so that the life-history of the organism may be 

 considered as consisting of the human or fever cycle and 

 the mosquito or flagellum cycle. 



In the human or fever cycle the parasites invade, the 

 blood corpuscles themselves, and develop within them, 

 finally sporulating after having demolished their host. In 

 the mosquito or flagellum cycle the parasites are free, or 

 are contained in a species of sheath, from which they soon 

 free themselves, and then, by virtue of their motility, propel 

 themselves into the tissues of the mosquito, where they 

 remain quiescent. Up to the present, we believe the 

 parasite has not been actually demonstrated in the mos- 

 quito in its quiescent stage, but this will probably be done 

 ere long. The mosquito dies soon after depositing its eggs, 

 and its body will probably fall into water, to which it goes 

 to lay its eggs ; and thus the quiescent parasites may enter 

 the intermediate host, man, in drinking-water; or, again, 

 the body of the mosquito may dry up, and, becoming dust, 

 may be inspired. In connection with this latter possibility, 

 it is to be remembered that it is said that malaria is apt 

 to manifest itself if the surface of the soil is disturbed. 



Varieties of the Malarial Parasite. — It has only been 



