419 



continent. During the seventeenth century, that zone extended farther 

 north up to the 23d parallel and southward to the parallel^ of Bahia and 

 Pernambuco. Finally, in 1850, it reached Rio de Janeiro. 



2. The transportation of mosquitoes of the yellow fever species, in 

 sailing vessels, appears to have been of frequent occurrence, ever since the 

 early times of the discovery of America. To it must, probably, be attributed 

 the coincidence of the severe epidemic of the so-called "modorra 

 pestilencial" in Santo Domingo, in 1494, with another very fatal epidemic 

 of the same name, in the Canary Islands, the same year. Apart trom the 

 conveyance of contaminated mosquitoes, healthy ones must have been 

 frequently imported into subtropical countries, where they are found now 

 to exist, having acclimated themselves to their new abodes. This is known 

 to be the case in Italy, in the south of Spain and coasts of the 

 Mediterranan, as well as in the South of the United States and in other 

 countries. The previous existence of the yellow fever mosquito must be 

 considered, per se, to constitute a dangerous complication whenever a case 

 of yellow fever happens to be introduced in a place usually free from that 

 infection. 



3. The range of the Andes and its prolongation along the Isthmus of 

 Panama and Central America, appears to have stood as a barrier 

 protecting to some extent the western coast of America against the 

 migration of contaminated mosquitoes. That obstacle, however, is about 

 to disappear when the Panama or the Nicaragua canal comes to be opened ; 

 let us hope, therefore, that, by that time, through the joint efforts of all 

 the nations interested, all the existing foci of the disease will have been 

 extinguished and that the adoption of measures, similar to those which 

 have proved so successful in the hands of our sanitary department, will 

 henceforth provide reliable means for controlling the propagation of yellow 

 fever. 



