288 FLIES AND DISEASE 



was present in the blood, and it only remained 

 to ascertain its mode of transmission. A common 

 local mosquito, called Stegomyia fasciata, seemed to 

 be the insect most likely to carry the disease, and 

 experiments on persons who offered themselves were 

 conducted with the most rigorous precautions 

 against any external contamination. A house was 

 constructed and rendered mosquito-proof by wire 

 gauze, and divided into two halves by a partition 

 of the same material. On the one side persons 

 occupying the room slept between soiled bed- 

 linen from yellow fever patients, etc. Into the 

 other half only carefully sterilized material was 

 allowed to enter, but in addition mosquitoes that 

 had fed previously on yellow fever patients were 

 introduced. A volunteer who entered this half 

 of the house was bitten and shortly afterwards 

 developed a typical attack of yellow fever, whilst 

 persons who occupied the other half of the house 

 for at least twenty days remained healthy. 



By such experiments the important truth was 

 established that yellow fever is only conveyed by 

 means of mosquitoes. It was further shown that 

 the mosquitoes only become infective twelve days 

 after feeding on a patient, indicating that as in 

 Malaria the parasite undergoes some developmental 

 changes in the mosquito. 



These facts once firmly established the Com- 

 missioners studied the life-history of the mosquito, 

 and based preventive measures on their researches. 



