128 



Insects and Disease 



was completely divided by a wire screen from floor 

 to ceiling. In one room fifteen mosquitoes that 

 had previously bitten yellow fever patients and had 

 undergone the proper period of incubation were 

 liberated. In this room a non-immune exposed 

 himself so that he was bitten by several of the in- 

 sects. A little later the same day and again the 

 next day the mosquitoes were allowed to feed on 

 him for a few minutes. Five days later, the usual 

 incubation period, he developed yellow fever. 



At the same time that he entered the building 

 two other non-immunes entered the other compart- 

 ment where they slept for eighteen nights separated 

 from the mosquitoes by the wire screen. They 

 showed no signs of taking the fever. 



In another mosquito-proof house two soldiers 

 and a surgeon, all non-immunes, lived for twenty- 

 one days. From time to time they were supplied 

 with soiled articles of bedding, clothing, etc., di- 

 rect from the yellow fever hospital in the city. 

 These articles had been soiled by the urine, fecal 

 matter and black vomit obtained from fatal and 

 other cases of yellow fever. These articles were 

 handled and shaken daily, but no disease developed 

 among the men and at the end of the twenty-one 

 days, two other non-immunes relieved them and 

 handled a new supply of clothing in the same way, 



