Insects and Disease 
632 
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 mosquitoes 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 experimentalists 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 diseases, or for one disease which manifests itself in several ways, 
due to the presence in the body of the infected patient of filariae or thread¬ 
worms. 
These organisms are of much higher organization than the minute unicel¬ 
lular Haemamoebae that cause malaria; they belong to the group of round- 
worms, the Nematoda, and in fully developed condition some species of 
filariae are very long, the notorious guinea-worm, Filaria medinensis, which 
parasitizes the human body in the tropics of the Old World, attaining a 
