SIR RONALD ROSS 



257 



case of the parasitic nematode filaria — suggested, 

 as a working theory of malaria, that the plasmodium 

 was carried by mosquitoes. This belief, not itself 

 new, he made current coin. He observed that there 

 is a flagellate form of the plasmodium, which only 

 comes into existence after the blood has left the 

 body : and he suggested that the flagella might 

 develop in the mosquito as an intermediate host, a 

 halfway-house between man and man. Then, in 

 1895, Surg.-Maj. Sir Ronald Ross, I. M.S., set to 

 work in India, keeping and feeding vast numbers of 

 mosquitoes on malarial blood ; and for two years 

 without any conclusive result. About this time 

 came MacCallum's observations, at the Johns 

 Hopkins University, on a parasitic organism, 

 halteridium, closely allied to the plasmodium 

 malariae ; he showed that the flagella of the 

 halteridium are organs of impregnation, having 

 observed that the non-flagellated form, which he 

 regarded as the female, after receiving one of the 

 flagella, changed shape, and became motile. In 

 August 1897, Sir Ronald Ross found bodies, con- 

 taining pigment like that of the malarial parasite, 

 in the outer coat of the stomach of one kind of 

 mosquito, the grey or dapple- winged mosquito, that 

 had been fed on malarial blood. In February 1898, 

 he was put on special duty under the Sanitary 

 Commissioner with the Government of India, to 

 study malaria, and started work again in Calcutta : — 



M Arriving there at a non-fever season, he took 

 up the study of what may be called 'bird malaria.' 



R 



