A Round-up of Undesirables 139 



by a particular species of mosquito called 

 Stegomyia, which sucks blood and the parasite 

 from the patient and transfers it to persons 

 whom he may later visit. 



There is a very fascinating story in the dis- 

 covery of the yellow-fever mosquito and his 

 significance to man, but we cannot tell it here. 

 We may only say that when they screened 

 the mosquito away from the fever patients 

 so that he could not get infected blood, they 

 stamped out yellow fever in Havana, and 

 can control it anywhere by keeping tab on 

 Stegomyia. 



It is sadly aggravating to the scientific 

 folk to realize that though they can get an 

 infected mosquito which they know contains 

 the deadly infective parasite somewhere in 

 his interior, no cultivating, no microscoping 

 or any other scrutiny has succeeeded in 

 recognizing the living thing which must be 

 right under their eyes. It probably is a 

 protozoan, and it is demonstrably so small 

 that the most powerful microscopes fail to 

 reveal it. It seems to be one of a very baf- 

 fling group of living beings causing disease, 



