334 READINGS IN BIOLOGICAL SCIENCE 



fever, but had been unable to prove it. This person was Dr. Carlos J. Finlay, 

 of Havana, who had advanced the mosquito theory in 1881. 



Walter Reed and his associates decided to investigate this theory not only 

 because they had observed that the mosquito's habits tally with the spread 

 of the disease, but also because of one peculiar fact about the infection of 

 houses. This fact was the length of time that it takes to change a nonin- 

 fected house to an infected. 



SIXTH CLUE 



A picture story of what happens when a case of yellow fever breaks out 

 in a house is given on the following page. 



In this picture it is shown that A's house was not infected with yellow 

 fever for 1 5 days after A came down with the fever, because people could 

 go there and not take it. But after the 1 5 days were up, everyone who went 

 there took the disease in from one to six days. 



What were the germs doing, and where were they, before they finally 

 infected the house? Walter Reed suspected they were being entertained in 

 the stomach of a mosquito, and stayed there until they were capable of pass- 

 ing on the disease through the mosquito's bite. 



As it was then believed that yellow fever could not be given to animals, 

 the only way of investigating it was to experiment on human beings. This 

 meant a tremendous responsibility for the members of the Board. They 

 agreed they must experiment on themselves as well as on the men who 

 volunteered for inoculation. Think of the high courage of the men who 

 took this great responsibility, and the gallantry of the American soldiers 

 who accepted the risk of suffering, or even death. These men were heroes 

 in the greatest war of all, the war against disease. 



THE FIRST EXPERIMENTS 



The first experiments were made in August 1900. Eleven persons were 

 subjected to the bite of mosquitoes of the species Aedes aegypti (for- 

 merly called Stegojnyia fasciata) after these mosquitoes had already 

 bitten patients with well-marked cases of yellow fever. Of these 1 1 per- 

 sons, two developed the disease. One of the positive cases was that of Dr. 

 James Carroll, a member of the Board. Both cases recovered. In one of these 

 cases it was proved that the infection could have been received in no other 

 way than by the bite of the mosquito. A third case developed later, ac- 

 cidentally. 



On September 13, 1900, Dr. Jesse W. Lazear, while visiting a yellow 

 fever hospital, was bitten. He dehberately allowed the mosquito, which 

 had settled on the back of his hand, to remain until it had satisfied its hunger. 

 Five days after the bite he came down with yellow fever of which he died, 

 a true martyr to science. From these three positive cases Walter Reed and 



