Atmospheric Temperature as an Essential Factor in the 

 Propagation of Yellow Fever x ) 



XIV INTERNATIONAL CONGRESS FOR HYGIENE AND DEMOGRAPHY 

 Berlin, Sept. 23=29, 1907 



Few events in medical science have the privilege of being so carefully 

 and thoroughly investigated by highly competent experts from scientific 

 institutions of different Nations, and under varied conditions of 

 geographical site and tropical surroundings, as have been the findings 

 of the U. S. Army Yellow Fever Commission of Habana in 1900 and 1901, 

 confirmatory of my mosquito theory of yellow-fever transmission. And so 

 unanimous has been the consensus of opinion among all subsequent 

 investigators regarding the fact that the bites of the "stegomyia calopus" 

 constitute the regular channel through which the disease is normally 

 trasmitted from man to man, that all the Governments directly interested 

 in the matter have agreed to consider that principle as the only sound 

 basis for an efficient prophylaxis of the disease. 



The time has come, therefore, when further investigations should be 

 made into the secondary factors which are known either to inhibit or to 

 intensify the faculty possessed by the stegomnia of first becoming 

 contaminated with the immature germs contained in the blood of a yellow 

 fever patient and of thereafter inoculating the matured germ to non-im- 

 munes. Above all should our attention be directed to the modus operandi of 

 atmospheric temperature which has at all times been responsible for the 

 yearly alternations of an epidemic and a non-epidemic season in the 

 endemic centres of former days, when the disease was allowed to pursue its 

 natural course unhampered by human interference of any kind. 



As far back as 1882 and 1883, having doubt in my mind as to the fact 

 that the stegomyia calopus or fasciata was the natural transmitter of 

 yellow fever, I had taken much pains to determine the influence of 

 atmospheric temperature on the functional activity of that species of 

 mosquito, then known in Havana as the Culex mosquito (Robineau Des- 

 voidy) ; and by a series of careful experiments I endeavoured to ascertain 

 for that insect the five temperature-limits which Van Tieghem, in his 



1) A pamphlet and published in the book of the transactions of the Congress. 



