632 Insects and Disease 



of yellow fever. Not a single one of the seven inhabitants of the house was 

 attacked by the disease. 



Another similar building was erected near by, well provided with doors 

 and windows for thorough ventilation. It was divided into two rooms 

 by a wire-screen partition extending from floor to ceiling. All articles 

 admitted to the building were carefully disinfected by steam before being 

 placed therein. Into the large room of this building mo.squitocs which had 

 been previously contaminated by biting yellow-fever patients were admitted. 

 Non-immunes were placed in both rooms. In the room in which mosquitoes 

 were not admitted the e.xperimentalists remained in perfect health. In 

 the other room six out of seven persons bitten by infested mosquitoes came 

 down with yellow fever. In all, of persons bitten by infested mosquitoes 

 that had been kept twelve days or more after biting yellow-fever patients 

 before being allowed to bite them, 80 per cent, were taken with the disease. 



Other similar crucial tests were made by the Commission and have been 

 made by other investigators working in other places. The conclusions are 

 positive. Yellow fever is caused by a germ, as yet undetermined, which 

 lives for part of its life in the blood of human beings, and is carried from 

 man to man by mosquitoes, being sucked up with blood by mosquitoes which 

 find access to yellow-fever patients, and transmitted to the blood of new 

 subjects from the beak during puncturing. An interval of about two weeks 

 after the mosquito is affected is necessary before the mosquito is capable 

 of conveying the infection, which means that the yellow-fever germ is under- 

 going a certain necessary part of its development in the mosquito's body. 



As I have already mentioned (p. 308), the mosquito species Stegomyia 

 jasciata, the carrier of the yellow fever in the West Indies, is the most abundant 

 mosquito species in the Hawaiian Islands and also in the Samoan Islands. 

 In neither of these groups of tropic islands has yellow fever yet found a 

 footing, but is it not possible that with the cutting of the Panama Canal and 

 the direct passage of ships from the West Indies to these islands, the whole 

 passage being made within tropical regions, yellow-fever-infested mosquitoes 

 will be carried alive to the Pacific islands? It is certainly a matter which 

 must receive scientific attention. 



Mosquitoes and filariasis. — Filariasis is the rather generic term for a 

 number of disea.ses, or for one disease which manifests itself in several ways, 

 due to the presence in the body of the infected patient of filarioe or thread- 

 worms. 



These organi.sms are of much higher organization than the minute unicel- 

 lular IIa>mama?b;c that cause malaria; they belong to the group of round- 

 worms, the Nematoda, and in fully developed condition some species of 

 filarial are very long, the notorious guinea-worm, Filaria medincnsis, which 

 parasitizes the human body in the tropics of the Old W'orld, attaining a 



