SANITATION OF THE PANAMA CANAL ZONE. 747 



tropical diseases to a limited extent. Eighteen months from the 

 present time, I am informed by the chief engineer, we will probabl^y 

 have on the Isthmus a force of some 15,000 men. Estimating from 

 our present ratio, I am inclined to think that not more than 2,000 of 

 these will be Caucasians and the other 13,000 negroes. Now, the 

 sanitary problem will be to protect these 15,000 men from malaria 

 and from yellow fever. I will take up first yellow fever. I assume 

 it as acce[)ted that it is conveyed from man to man only by the 

 female Stegomyia,, who has previously bitten some human being 

 suffering from yellow fever. Therefore, given a place in which there 

 are no infected Stegomyia^ yellow fever can not originate until a 

 human being suffering from yellow fever has been introduced and 

 infected the local Stegomyia., or unless the female Stegomyia^ infected 

 at some distant point where yellow fever prevails, has been intro- 

 duced. Practically the first is almost the only method of infecting a 

 locality — namely, the introduction of a human being suffering from 

 yellow fever. The city o-f Panama has been in the condition for a 

 great many years of at all times having within her borders some 

 infected Stegomyia at all seasons of the year, and the nonimmune 

 foreigner coming within her limits is liable to contract the disease. 

 Yellow fever is at present endemic nowhere on the Zone except in 

 the city of Panama. The object of the sanitarian is, therefore, to 

 get rid of the infected Stegomyia at present existing in the city, and 

 this can be done in this way: Establish a system whereby the health 

 authorities will pretty certainly be informed of every case of yellow 

 fever occurring; then take the house in which this case occurs and 

 fumigate it, so as to destroy all the mosquitoes within its borders. 

 Do the same with all the contiguous houses. 



This, it has been found by experience, kills all the infected mos- 

 quitoes at that particular focus. The same thing is done at every 

 other focus as yellow fever occurs. Gradually, in this way, all the 

 foci in the connnunity are destroyed; and when you have destroyed 

 your last focus yellow fever is at an end. Or, if you want to be 

 more expeditious and the town is not too large, you can systematic- 

 ally fumigate every house in the town, and thus pretty certainly 

 destroy all infected mosquitoes and do away with yellow fever nuich 

 more rapidly. But no system of reporting is ever absolutely certain 

 and the sanatarian should see that other very important adjuncts 

 to the fumigation work are carried on at the same time. The 

 Stegomyia is a house mosquito and cleanly in her habits, seeks prin- 

 cipally clean rain-water barrels and water containers, and lives very 

 close to her birthplace, not traveling far. Therefore, as an addi- 

 tional sanitary safeguard, every receptacle for water should be so 

 screened and, covered that mosquitoes can not liave access. All 



