Br Stephens, The Prevention of Malaria. 123 



The Prevention of Malaria. By J. W. W. Stephens, M.D., 

 Gonville and Caius College 1 . 



[Received 25 February 1901.] 



The various hypotheses put forward as to the nature of the 

 crescentic and flagellating forms of the malaria parasite, and 

 the suggestions made, originally by Laveran and subsequently 

 by others, a,s to the possible role of mosquitoes in the transmission 

 of malaria need not be considered here. We may pass directly 

 to the actual work which has resulted in our present knowledge 

 of the relation of mosquitoes to malaria. Ross, in India, at 

 Manson's instigation, worked at the question whether parasites 

 further developed in the gut of mosquitoes. He worked 

 principally with Proteosoma of birds' blood, and for these 

 parasites worked out very fully their complete cycle in the 

 mosquito from the first stages in the stomach-wall to the final 

 stage of sporozoites in the salivary glands. He further was 

 able to shew that the parasites could be transmitted to healthy 

 birds by means of mosquito punctures (in fact by inoculation of 

 the sporozoites). Here then was at last the complete proof for 

 birds of what had been for long a matter of speculation with 

 regard to human malaria. 



Ross had seen earlier in the gut of certain mosquitoes 

 that had bitten malarial patients pigmented bodies which he 

 considered to be further stages in the development of the human 

 parasite, but this could not then be proved. In the meantime the 

 Italians had been working at the question from different points 

 of view. It was shewn by Grassi that the distribution of Anopheles 

 claviger bore a close relation to the distribution of malaria, that 

 in fact it was always present most plentifully in those regions 

 where malaria was most severe; whereas Culex pipiens and other 

 varieties of Culex were more frequent in regions not infested with 

 malaria and were often absent in malarial regions. Bignami, who, 

 since 1894, had been trying to infect patients with malaria by 

 mosquito-bites had always failed, but now, using mosquitoes from 

 malarial regions, he eventually succeeded; the result was certainly 

 a fortunate one, for among the mosquitoes used, Anopheles were 

 very few. 



But the fact was established; and later Grassi, Bastianelli 

 and Bignami worked out the cycle of development of the human 



1 Most of the data on which this paper is based will be found in 



1. Reports to the Malaria Committee of the Royal Society, 1899-1900, by 



J. W. W. Stephens, M.D. Cantab., and S. E. Christophers, M.B. Vict. 

 (Harrison and Sons, London). 



2. Further Reports to the Malaria Committee, 1900 (Harrison and Sons). 



3. Reports. Third Series, 1900 (Harrison and Sons). 



4. Reports. Fourth Series, 1901 (Harrison and Sons). 



