2i 6 Master Minds of Modern Science 



of the twentieth century was the most dreaded enemy of 

 the British Empire — an enemy before which army, navy, 

 and doctors were powerless. 



Sir Patrick Manson was a Scottish doctor, born near 

 Aberdeen, who in 1866 went out to become medical officer 

 at a Chinese hospital in Formosa. There he studied 

 elephantiasis, the strange disease which causes legs and 

 arms, or other parts of the body, to assume monstrous 

 proportions. And there he was first brought into contact 

 with malaria at close quarters. 



A theory then generally held was that elephantiasis, a 

 tropical disease like malaria, was caused by the night air 

 of marshes. Manson began his investigations, and came 

 to the conclusion that the presence in human blood of a 

 parasite called the filaria worm probably had some con- 

 nexion with the disease. But the discovery only raised 

 a greater problem. How did the filaria worm get into the 

 blood ? The worm could neither walk nor fly. A possi- 

 bility was that it was sucked up by something that fed 

 upon human blood, then released again into the bodies of 

 previously uninfected persons. 



The evidence pointed to the mosquito, which in biting 

 a person infected with the germs of elephantiasis, and 

 then passing on to uninfected persons, might well spread 

 the disease. To test this theory, Manson examined the 

 blood of some of his native helpers at the hospital. 

 Finding one who was heavily infected, he induced him to 

 sleep in a room containing mosquitoes and to let them 

 bite him. 



The next morning Manson collected the insects, gorged 

 with the blood of the infected boy. He dissected them 

 and examined them under a microscope. They were all 

 infected with live filaria worms. Thus was it discovered 

 that the mosquito was the carrier of the germ which 

 caused elephantiasis. 



Manson's discovery set certain men thinking. If the 



