HISTORY 



carrier of malaria, a suggestion which we have already noted to be present 

 at the dawn of written medicine. In 1884 Laveran pointed out that Hanson's 

 researches on filariasis opened a possibility that malaria might be conveyed 

 in the same way, but these suggestions did not lead to anything, and it was 

 not till Manson, in 1894, emphasized the importance of this possibility that 

 any serious notice was taken of the problem involved. In 1898 Ross, working 

 on Hanson's hypothesis, discovered the important fact that the malarial 

 parasite could grow in the stomach of a mosquito, and eventually traced out 

 the whole cycle of the parasite of bird malaria in that insect, and this was 

 subsequently completed as regards the human parasite by Grassi, and con- 

 firmed by Harchiafava and Bignami with regard to the infection in man. 



Experimental proof of the truth of this carriage was effected by Hanson 

 producing typical attacks of malaria, in persons who had never left England, 

 by anopheline mosquitoes infected with the parasites in Italy, and by Low 

 and Sambon living during the malarial season in the Roman Campagna, with 

 no other protection except good anti-mosquito measures, and failing to 

 become infected with the disease. 



We therefore have reached this stage of knowing the parasitic cause and its 

 life-cycle in man and the mosquito, but there are some things which we do 

 not know, and these are the reason of the persistence of the infection, in spite 

 of quinine therapy, in some people, while others are without doubt cured, 

 and the reason why the disease appears at times as epidemics. There can be 

 no doubt that the realization of a reservoir for the disease is most important, 

 and there is equally no doubt that this reservoir is man, especially native races, 

 and perhaps more especially the children of native races. 



The following additional points appear to us to require further study : — 



I. The form in which the malarial parasite lies dormant in the human body 

 (with special reference to the parthenogenesis of the macrogametocyte) . 



The question of parthenogenesis is still much debated. Neeb has investi- 

 gated it in L, malarics, and has contrasted it with the schizont stage of the 

 same parasite as follows : — \ 



Character. 



Segmenting Macrogametocyte. 



Schizont. 



Size 



Shape . . 

 Chromosomes . , 



Cytoplasm 

 Haemozoin 



Almost fills the erythro- 

 cyte. 



Oval, not quite centrally 

 situated. 



Large, coarse, purplish- 

 brown in red-violet basis, 

 which runs in a band-like 



, curve along periphery. 



Resembles that of a typical 

 macrogametocyte. 



Coarse yellowish - brown 

 granules excentrically 

 placed . 



Fills about two-thirds of 

 the erythrocyte. 



Circular, and centrally situ- 

 ated. 



Small, fine, separate, pur- 

 ple, arranged in a circle 

 around the haemozoin. 



Resembles that of the tro- 

 phozoite. 



Fine, dark brown or black 

 granules, usually concen- 

 trated into one centrally 

 placed clump. 



Thompson believes that Schaudinn probably mistook for parthenogenesis 

 a double infection of a corpuscle with a gametocyte and a schizont. 



Ross believes that the ordinary asexual forms persist in the blood in small 

 numbers, and, undergoing schizogony, are sufficient to account for the in- 

 definite persistence of the infection. Karrewij has found parthenogenesis to 

 occur in P. vivax at the height of the febrile attack. 



2. Whether Schaudinn is correct in believing that the eggs of the mosquito 

 can become infected, and, if so, whether that infection is capable of being 

 spread by the next generation of mosquitoes. 



