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APPLIED BACTERIOLOGY 



though the evidence seems to point to this. Golgi and 

 Canalis admit the existence of five distinct varieties of 

 parasites; Grassi and Felleti only two; while Laveran 

 himself was of opinion that there was only one parasite 

 in varying forms. 



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

 established that Dr. Hanson'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. 



In the quartan type of the spring fevers, the parasite is 

 found in the blood in all forms during the entire length of 

 the attack. The sporulating forms consist of seven to ten 

 spores arranged in rosette form, while in the spring tertian 

 all forms, with the exception of the youngest, are profusely 



