146 MALARIA 



The foregoing account of this varied and romantic 

 life-history is no hypothetical one. With the excep- 

 tion that, so far as we know, no one has yet seen 

 the blasts enter the corpuscles and become amcebulae, 

 every stage in the story has been verified over and over 

 again by competent observers, and their observations 

 are now accepted by all whose opinion in such matters 

 has weight. Further, the facts here recorded are not 

 peculiar to parasites in man. Allied forms of Protozoa 

 attack other vertebrates, and, in fact, the first haema- 

 tozocJn whose life-history was thoroughly worked out 

 by Ross was the Hcemamoeba {Proteosoma) relicta, which 

 causes a malaria-like disease in birds, and is conveyed 

 from one bird to another by means of the common 

 gnat, Culex pipiens. Again, the parasite which causes 

 so much loss to stock-owners, the Texas fever organ- 

 ism, Pyrosoma bigeminum, is, thanks to the researches 

 of Smith and Kilborne, now known to be conveyed 

 from one ox to another by the cattle-tick, Boophilus 

 bovis. Thus, however strange the life-history of the 

 malarial parasite may seem to the unscientific, it is 

 very much what might have been expected by zoolo- 

 gists who have worked on allied organisms, and it is 

 vouched for in its main features by the most expert 

 workers in England, France, America, Italy, and 

 Germany. The whole literature of the subject of 

 transmission of disease by insects has been ably sifted 

 and brought together by Dr. Nuttall in a monograph 

 whose title is mentioned in the Bibliography. 



For two years and a half Major Ross dissected 

 mosquitoes, looking for traces of the malaria organism 

 and finding none, but at last found what he sought in 

 a species of mosquito that had hitherto escaped his 

 attention. This means that, like most other parasites, 

 the Haemamoebidae will develop in one kind of animal 

 and in one kind only. If taken up by another kind 

 they are simply digested. The mosquito with the 



