712 INFECTION AND IMMUNITY. 



The Southern States were invaded repeatedly in 

 the last decade of the eighteenth century, in 1803, 

 1805, 1853, 1867, 1873, 1878, 1905, and in lesser 

 degrees at other times, in all ninety-six times. The 

 severest epidemics were those of 1853 and 1878. 



^ Q man y m i cr bes which have been cited as the 

 cause of yellow fever need not be described. The 

 Bacillus icteroides of Sanarelli, which had at- 

 tained more prominence than any other, was shown 

 by Sternberg, by Eeed and Carroll and by the more 

 recent work on the mosquito theory, to bear no 

 causal relationship to the disease. According to 

 Reed and Carroll it is identical with the hog-chol- 

 era bacillus. 



The monumental work of Reed, Carroll, Agra- 

 monte and Lazear (1900), the last of whom lost 

 his life from yellow fever, has made it possible 

 to replace accurate knowledge of the epidemiology 

 and prophylaxis of yellow fever and, to a certain 

 extent, of its etiology, for many incorrect ideas 

 which had prevailed up to that time. 



The Mosquito The conception that yellow fever is transferred 

 Theory. -f rom one p erson to another by mosquitoes was 

 first advanced positively by Carlos Finlay, a 

 Cuban physician, in 1881, although several Ameri- 

 can physicians had long before noted the preva- 

 lence of mosquitoes during yellow fever outbreaks 

 (Rush, 1793; Weightman/ 1839 ; Wood, 1853; 

 Barton, 1853). Finlay reported the transmission 

 of the disease, experimentally, by the bites of mos- 

 quitoes which had fed on yellow-fever patients, 

 and stated that light attacks which followed the 

 bites resulted in the establishment of immunity. 

 The subsequent observations of Reed and his co- 

 workers indicate, however, that Finlay's technic 



