204 Arthropods as Hosts of Pathogentc Protozoa 
fever. Nothing could better serve as the fomites which were sup¬ 
posed to convey the dread disease. 
Three non-immunes unpacked these articles, giving each a 
thorough handling and shaking in order to disseminate through the 
air of the room the specific agent of the disease. They were then 
used in making up the beds which the volunteers occupied each night 
for a period of twenty days. The experiment was repeated three 
times, volunteers even sleeping in the soiled garments of yellow fever 
victims but in not a single case was there the slightest symptom of 
disease. The theory of the spread of yellow fever by fomites was 
completely demolished. 
The infected mosquito building, equal in size to its companion, 
was the antithesis as far as other features were concerned. It was 
so constructed as to give the best possible ventilation, and bedding 
which was brought into it was thoroughly sterilized. Like the 
infected clothing building it was carefully screened, but in this case 
it was in order to keep mosquitoes in it as well as to prevent entrance 
of others. Through the middle of the room ran a mosquito-proof 
screen. 
On December 5, 1900, a non-immune volunteer who had been in 
the quarantine camp for fifteen days and had had no other possible 
exposure, allowed himself to be bitten by five mosquitoes which had 
fed on yellow fever patients fifteen or more days previously. The 
results were fully confirmatory of the earlier experiments of the 
Commission-—at the end of three days, nine and a half hours, the 
subject came down with a well marked case of yellow fever. 
In all, ten cases of experimental yellow fever, caused by the bite 
of infected mosquitoes were developed in Camp Lazear. Through¬ 
out the period of the disease, other non-immunes slept in the little 
building, separated from the patient only by the mosquito-proof 
screen, but in no circumstances did they suffer any ill effects. 
It was found that a yellow fever patient was capable of infecting 
mosquitoes only during the first three or four days after coming 
down with the disease. Moreover, after the mosquito has bitten 
such a patient, a period of at least twelve days must elapse before 
the insect is capable of transmitting the disease. 
Once the organism has undergone its twelve day development, 
the mosquito may remain infective for weeks. In experiments of 
the Commission, two of the mosquitoes transmitted the disease to a 
volunteer fiftv-seven davs after their contamination. No other 
