INSECTS AND MANKIND 435 



forty thousand fatal cases being recorded in New Orleans 

 alone. Until 1900 yellow fever was generally believed to 

 be " due to some insidious poison borne by the air and 

 introduced into the human body, probably through the 

 respiratory system." Consequently efforts were made to 

 fight the disease by " methods of quarantine, burning, and 

 fumigation . . . that destroyed an enormous amount of 

 property, including valuable cargoes, and paralysed the 

 business and social activities of great cities." Such observed 

 facts as the carriage of infection dov/n the wind, though 

 never for a great distance, suggested the likelihood of blood- 

 sucking insects as transmitters, and the part played by 

 Aedes argenteus was convincingly demonstrated by W. Reed 

 in Cuba during 1900. In the succeeding year by the drain- 

 ing or oil-filming of the mosquitoes' breeding-places, yellow 

 fever was definitely stamped out in Havana, which had 

 during the nineteenth century suffered a yearly mortality 

 often exceeding a thousand. A few years later the import- 

 ance to mankind of the knowledge of the part taken by 

 insects in carrying disease-causing organisms, was most 

 strikingly demonstrated in Panama. For many decades 

 work on the long-projected canal through the Isthmus had 

 been held up, far less by engineering difficulties than by 

 the prevalence of yellow fever and malaria among the 

 engineers, managers, and workmen, for the " Canal zone 

 was formerly one of the most unhealthful places on earth." 

 By the use of proper precautions and the elimination of 

 mosquito breeding-haunts, under the supervision of W. C. 

 Gorgas, the total mortality among the white Americans 

 inhabiting the zone was reduced to 9*72 a thousand, '' a 

 rate no higher than for a similar population in the healthiest 

 localities in the United States." Few stories of human 

 enterprise afford more convincing evidence than this of the 

 powerful hindrance which can be offered to man's designs 

 by the action of insects so long as their harmful influence 

 remains unknown, or of the power of mankind to overcome 

 such hindrance after a knowledge of its course and nature 

 has been acquired. 



