1900.] on Malaria and Mosquitoes. 309 



1898, Dr. Daniels of the Malaria Commission of the Royal Society 

 and the Colonial Office, arrived in Calcutta to examine and report 

 upon my results. After carefully repeating the various experiments 

 he fully confirmed the statements made by me.* At the same 

 moment, the work was taken up with great brilliance and success by 

 Dr. Koch and by Prof. Grassi and Drs. Bignami and Bastianelli, in 

 Italy. I must now describe the investigations of these observers — 

 though I have scarcely space to do so at the length they deserve. 



Ever since the discoveries of Laveran and Golgi, the Italian 

 observers of the Roman school have done much important work on 

 malaria, facilitated by the well-known prevalence of the disease near 

 Rome ; work, if not of much originality, yet full of careful detail. 

 More recently, however, this work had been practically arrested by 

 their theory — wholly gratuitous, but which they accepted as a dogma 

 — that the motile filaments are forms of disintegration in vitro. When 

 Manson propounded his theory, Bignami, for instance, rejected it on 

 this ground. But at the same time he evolved a gnat-theory of his 

 own — a theory that malarial fever is inoculated by gnats which carry 

 the parasite from marshy areas. The arguments he used were the 

 epidemiological ones already advanced by King, and which can 

 scarcely be said to amount to more than a plausible hypothesis : the 

 only solid basis for the theory — that of Manson — was opposed by 

 him. Later, however, the work of Simond, Schaudinn, Siedlecki, 

 MacCallum and myself, explained by Manson, rendered the Italian 

 position concerning the motile filaments quite untenable ; and 

 Bastianelli, Bignami and Grassi now undertook a study of the 

 mosquito-theory on sound principles. My own results, with descrip- 

 tions of the technique employed and with illustrations of the zygotes, 

 had been published from time to time ; a summary of them had been 

 given by Manson in June 1898, and another, including the infection 

 of healthy birds, before the British Medical Association, early in 

 August ; and there could therefore be no difficulty in following up 

 the observations therein recorded. In September, Grassi published, 

 a paper in which he described certain investigations made in Italy 

 with a view to ascertaining the species of gnats which are associated 

 with the prevalence of malaria in that country. Such investigations 

 are not, I think, trustworthy ; and as a matter of fact two out of the 

 three species of gnat then selected by Grassi as being malaria-bearing 

 ones, have now been rejected by him. The third species was an 

 Anopheles, namely A. claviger, Fabr. 



At the same time Bignami resumed his study of the subject. 

 Some years previously, following his theory, he had endeavoured to 

 infect healthy persons by the bites of gnats brought from malarious 

 places. He had failed and abandoned his efforts — and I believe that 

 his method would of itself never had led to a solution of the problem. 

 In the autumn of 1898, however, he renewed his efforts ; but was 



* Nature, August 3, 1899. 



