204 Arthropods as Hosts of Pathogenic 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 yeUow fever 

 victims but in not a single case was there the slightest sjmiptom 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 sufEer 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 fifty-seven days after their contamination. No other 



