TRANSMISSION OF YELLOW FEVER RY MOSQUITOES. 



By George M. Sternberg, M. D., LL. D. 



Snr(/coti-(T('iier((l United Stairs Ariiiji. 



The discoveries which hiive been made during the past twent3"-five 

 years with reference to the etiology of infectious diseases constitute 

 the greatest achievement of scientific medicine and afford a substantial 

 basis for the application of intelligent measures of proph3daxis. We 

 now know the specific cause (germ) of typhoid fever, of pulmonary con- 

 sumption, of cholera, of diphtheria, of erysipelas, of croupous pneu- 

 monia, of the malarial fevers, and of various other infectious diseases 

 of man and of the domestic animals; ])ut up to the present time all 

 efforts to discover the germ of yellow fever have been without success. 

 The present writer, as a member of the Havana Yellow Fever Commis- 

 sion, in 1879, made the first systematic attempt to solve the unsettled 

 questions relating to yellow-fever etiology hy modern methods of re- 

 search. Naturally the first and most important question to engage ray 

 attention was that relating to the specific infectious agent, or germ, 

 which there was every reason to believe must ])e found in the bodies 

 of infected individuals. Was this germ present in the blood, as in the 

 case of relapsing fever; or was it to be found in the organs and tissues 

 which upon post-mortem examination give evidence of pathological 

 changes, as in typhoid fever, pneumonia, and diphtheria; or w^as it 

 to he found in the alimentary canal, as in cholera and dysentery? The 

 clinical history of the disease indicated a general blood infection. As 

 my equipment included the best microscopical apparatus made, I had 

 strong hopes that in properly stained preparations of blood taken from 

 the circulation of yellow-fever patients my Zeiss 1/18 oil immersion 

 objective would reveal to me the germ I was in search of; but I was 

 doomed to disappointment. Repeated examinations of blood from 

 patients in every stage of the disease failed to demonstrate the pres- 

 ence of micro-organisms of an}" kind. My subsequent investigations in 

 Havana, Vera Cruz, and Rio de Janeiro, made in 1887, 1888, and 1889, 

 were equall}^ unsuccessful. And numerous competent microscopists 

 of various nations have since searched in vain for this elusive germ. 

 Another method of attacking this problem consists in introducing ])lood 



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