454 SCIENCE PROGRESS 



active bodies then thought to be merely " flagella " ; but Manson now main- 

 tained that they were really flagellated spores, meant to infect mosquitoes 

 which bite infected men ; and he thought that the infected insects carry the 

 germs from men to the marsh, from which the germs infect healthy men 

 in exhalations — just the opposite of King's hypothesis. The Italians rejected 

 these ideas ; and none of the theorists made experiments on the subject, 

 though all of them could have done so. In 1895 D. Bruce showed that 

 certain trypanosomes of cattle are carried by tsetse flies. In 1895-7, I failed 

 to make the malaria parasites develop in mosquitoes of the genera Culex and 

 Stegomyia ; but in August 1897 succeeded in doing so in mosquitoes of the 

 sub-family Anophelina — which really proved the mosquito-theory, though 

 my work was interrupted for six months at the moment of success. At the 

 same time MacCallum and Opie in America showed that what Manson took 

 to be flagellated spores were really sperms — thus explaining certain details 

 of my observations. In 1898, not being able to work with human malaria, 

 I traced out the whole development of birds' malaria in mosquitoes, showed 

 that the parasites pass into the salivary glands of the insects, and infected 

 twenty-three out of twenty-eight healthy birds by the bites of mosquitoes — 

 and was then interrupted again by official duties. 



It was thus demonstrated that mosquitoes carry the germ, not from the 

 marsh to men nor from men to the marsh, but from man to man ; and in 1898- 

 9 the Italians, with full knowledge of my work, completed my observations 

 on human malaria and infected four healthy men in Rome by the bites of 

 mosquitoes. In 1899 I proceeded to Sierra Leone with E. E. Austen (of the 

 British Museum), H. E. Annett, and R. Fielding-Ould, completed my work 

 on human malaria, found the two chief malaria-bearing Amophelines of 

 Africa, demonstrated their habits, showed how it is that malaria is connected 

 with marshes, and worked out the details of my method of preventing malaria 

 by " mosquito-reduction " — these results being widely published in 1899- 

 1900. In 1900 P. Manson infected several volunteers in London by the bites 

 of mosquitoes brought from Italy. At the end of 1900 the Americans, Reed, 

 Lazear, Carroll, and Argamonte proved by direct experiments that yellow 

 fever is carried from man to man by Stegomyia as malaria is by Anophelines ; 

 and next year W. C. Gorgas commenced, under the orders of General Leonard 

 Wood, to banish both malaria and yellow fever from Havana by mosquito- 

 reduction. In 1901, also, seeing that little was being done in British posses- 

 sions, I went again to Sierra Leone with L. Taylor to give an object-lesson 

 on mosquito-reduction by means of privately subscribed funds ; and pro- 

 ceeded to Lagos, where the Governor, Sir William MacGregor, was starting 

 the same work ; and in that year similar excellent campaigns were com- 

 menced by Malcolm Watson in the Federated Malay States, and under F. 

 Clarke in Hongkong ; and the first volume of F. V. Theobald's classical mono- 

 graph on mosquitoes was published by the British Museum. In 1902 I went 

 for a third time to Sierra Leone ; and then with Sir W. MacGregor to Ismailia, 

 where the Suez Canal Company completely banished malaria by my method. 

 In 1903 A. Balfour began mosquito-reduction at Khartum. In 1904, on the 

 invitation of the American Government, I visited Panama, where the Canal 

 was being commenced, and met Gorgas at New York en route ; his results are 

 well known. In 1906, E. H. Ross began to clear Stegomyia mosquitoes from 

 Port Said ; and I visited Greece in that year, Mauritius in 1907 (with C, E. 

 P. Fowler), Bombay in 1909, and Spain, Greece, and Cyprus in 1913, in 

 which latter place R. A. Cleveland has made a notable reduction of malaria. 



I do not mention many local or temporary campaigns ; nor large cam- 

 paigns done chiefly on a quinine basis in Italy, Greece, and in French and 

 German possessions ; nor work carried on during the war ; nor numerous 

 abstract researches of various kinds. 



We should note that (i) the various theories enunciated up to 1894 



