CHAPTER XXIX. 

 GROUP VI. 



PROTOZOON INFECTIONS. 

 I. MALARIA. 



Etiology. The etiology of malaria, which for long was 

 supposed to be associated with impure and swampy 

 atmospheres (malaria is from ma? aria, Italian, 

 meaning bad air), remained unknown until 1880, 

 when Laveran discovered ameboid, half-moon 

 shaped and flagellated forms of a parasite in the 

 blood of the patients. In following years Golgi, 

 Grassi, Marchiafava and Celli and many others 

 took prominent parts in working out the different 

 forms of parasites, their sexual characters and their 

 relation to the different types of malaria. 



ROSS and The conception that mosquitoes may be influen- 

 tial in transmitting malaria is a very old one and 

 its origin is unknown. In 1894 Manson suggested 

 that the malarial organism may utilize the mos- 

 quito as an intermediate host where, after under- 

 going further development, it again becomes in- 

 fectious for man. He was inclined to think that 

 the flagella are reproductive forms, which are 

 essential for an extra corpus life of the parasite. 

 The proof of this came from MacCallum in 1897, 

 who showed that the flagellated forms are really 

 spermatozoites, the function of which is to im- 

 pregnate female cells of the parasite. This was 

 observed first in relation to halteridium, one of 



