274 



YELLOW FEVER 



And, short of such great enterprises as Govern- 

 ment works of drainage, much has already been 

 done, in many African towns, and in India, by 

 the work of a few men and women : not only by 

 practical sanitary improvements, but by insistent 

 teaching and lecturing. 



Before leaving the subject of malaria, it must be 

 added that the discovery and study of the parasite 

 which causes it have cleared up the mystery of the 

 specific action of quinine upon the disease. It 

 operates simply by its germicidal effect upon the 

 microbe. But, beyond this, we have now a clue 

 which we never had before to guide us to the most 

 advantageous manner of administering the drug. 



2. Yellow Fever. 



The specific organism of malaria may become 

 active again and again in the blood, causing 

 relapses twenty years or more after the original 

 infection. The specific organism of yellow fever 

 expends itself at once, in one acute attack ; and, 

 if the patient recovers, he is thenceforth more or 

 less immune against infection. In the case of 

 malaria, experiments on man were voluntarily 

 submitted to, only to prove that Anopheles carries 

 the disease : in the case of yellow fever, similar 

 experiments were voluntarily submitted to, not only 

 to prove that the disease is mosquito-carried, but 

 also to obtain immunity. That the inoculation of 

 the disease, by the application of a single mosquito 

 recently contaminated, is calculated to produce a 



