ETIOLOGY OF YELLOW FEVER 455 



attempts to find by microscopic examination the yellow fever 

 parasite, either in the blood of patients suffering from the 

 disease, or in the tissues of infective mosquitoes, have been 

 attended with negative results. 



Though nothing has been determined regarding the actual 

 nature of the virus, yet the results already obtained have 

 supplied the basis for preventive measures against the disease, 

 these being directed towards the destruction of mosquitoes and 

 the protection of those suffering from yellow fever, and also the 

 healthy, against the bites of these insects. Already a striking 

 degree of success has been obtained in Havana. Such measures 

 came into force in February 1901, and in ninety days the town 

 was free of yellow fever and for fifty-four days later no new 

 cases occurred; and although subsequently the disease was 

 reintroduced into the town, no difficulty was experienced in 

 stamping it out by the same measures. In recent years the 

 results have also been highly gratifying, and the disease may 

 be said to be practically eradicated from Havana. In other 

 places also successful results have been obtained, and epidemics 

 would appear to be now under control if the proper measures 

 are taken. 



