DAHLGREN, THE MALARIA MOSQUITO 



41 



Fabricius) which must previously have fed on the blood of a yellow fever 

 patient; that the fever could not possibly spread without the presence of 

 a mosquito, and that simple contact with a yellow fever patient was not 

 dangerous. To assure themselves of the correctness of their conclu- 

 sions, members of the commission in the course of their investigations 

 even went so far as to sleep for weeks in bed clothing soiled by yellow 

 fever patients. 



The organism which causes the yellow fever, has not, up to the present 

 time, been found ; but it is in every way probable that it will prove to be a 



FIG. 33. THE DISTRIBUTION OF STEGOMYIA. 



After Theobald. 



blood parasite of the class Sporozoa, its life-history resembling in a 

 general way that of the malarial organism. The period of incubation in 

 man, i. e., the period which must elapse between the bite of the infected 

 mosquito and the beginning of the sickness, varies from forty-one hours 

 to not more than six days. The period of its development 

 in the mosquito was found by the commission to be twelve T ncu b a tion 

 days or more. This fact is of very great importance in rela- 

 tion to quarantine measures, and makes it entirely possible to prevent 

 the introduction of yellow fever into any port where it does not exist. 



