DEVELOPMENT OF CONTROL MEASURES 51 



Flint having shown in 1868 that yellow fever was distinct 

 from malaria since its course was not affected by use of quinine, 

 Finlay, in 1882, announced his belief that the disease in some way 

 was transmitted by the mosquito. This theory was fully substan- 

 tiated in 1900-1902 by a board of U. S. Army medical officers, 

 who proved conclusively that Aedes calopus was the culprit. 

 Although the infective agent was not found, the discovery that 

 yellow fever, like malaria, is transmitted by the mosquito was 

 sufficient to make preventive work possible. 



BEGINNING OF MOSQUITO CONTROL 



The value of these two epoch-making discoveries was at once 

 apparent. Since both malaria and yellow fever were transmitted 

 in nature solely by mosquitoes, the only thing necessary to elimi- 

 nate both was to control the mosquito. This might be done 

 either by destroying the mosquito or by rendering it impossible 

 for it to get access to malaria or yellow fever patients — in 

 other words, by screening — or by a combination of both methods. 



These discoveries meant, to put it in another way, that two of 

 the chief obstacles to man's conquest of the tropics could be 

 brushed aside. They meant that no longer could these scourges 

 of humanity defy all sanitary and medical measures. They 

 meant that great engineering works like railroads, canals and 

 other modern necessities of trade could be carried through to 

 completion anywhere in the tropics. 



No delay took place in applying the newly gained knowledge. 

 The first great demonstration of its soundness was afforded in 

 1901, when Gorgas freed Havana, Cuba, from yellow fever in 

 3 months; the city had not previously been without yellow fever 

 for 150 years. In this classic campaign, both screening and 

 anti-mosquito methods were utilized. 



SANITARY CONQUEST OF THE CANAL ZONE 



But it was in the sanitation of the Panama Canal Zone that 

 Gorgas achieved his greatest triumph. Malaria and yellow 

 fever had disastrously defeated two attempts by the French to 

 complete the canal, so when the American government undertook 

 the great task, Gorgas was placed in charge of the anti-mosquito 

 work in the whole zone. 



Within a few months, yellow fever was almost eliminated. 

 The last case in the City of Panama was reported in 1905, while 



