THE CONQUEST OF THE MOSQUITOES 183 



was more, he thought that only one kind of mos- 

 quito was guihy of carr^^ing it. This was a Httle 

 gray mosquito that we call Aedes. 



Three doctors set to work to try out Dr. Find- 

 lay's idea. They tried it on themselves, since 

 they did not want to ask any one else to volunteer 

 for so dangerous an experiment. Dr. Carroll let 

 himself be bitten by an Aedes mosquito that had 

 first been allowed to bite a yellow-fever patient. 

 He came down with a severe case of yellow fever 

 from which he recovered. Dr. Lazear was also 

 bitten in the same way. He took yellow fever 

 and died the death of a brave man. 



All that year the doctors studied yellow fever 

 and mosquitoes and at the end of the year they 

 were.vSure of these facts: 



1. Yellow fever is carried by an Aedes mos- 

 quito that has bitten a yellow fever patient. 



2. It cannot be carried in any other way. 



In order to make Havana safe the Americans 

 had two things to do. They had to screen yellow 

 fever patients so that no mosquitoes could bite 

 them and carry the disease to other people, and 

 they had to kill off mosquitoes as fast as they 

 could. When these two things were done, there 

 was no more yellow fever in Havana, and by 

 watching the ships that sailed in from yellow 

 fever ports it was kept out. 



It happened that two years earlier an English- 

 man in India had found that malaria is also carried 



