Dr 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, as to the possible rSle 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. R. Christophers, M.B. Viet. 
(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). 
