First Sanitary Work 277 



in this manner were treated with oil. Sufficient 

 oil was used to cover the water surface com- 

 pletely. As the force became more experienced, 

 better control was established. 



In the early part of 1905 there was a large 

 number of non-immunes in the city of Panama, 

 and it became necessary to work with increased 

 vigor, because, even with a greatly reduced num- 

 ber of Aedes calopus, the chances for the spread of 

 yellow fever increased. 



The fumigation work proved the marked effects 

 that elimination of the containers had made on the 

 eradication of Aedes calopus by the decreased 

 number of dead insects found after fumigation. 

 Ultimately we controlled the situation to the 

 extent that but one per cent, of the houses were 

 producing larvae, and inspection work caused a 

 large percentage of larvae to be destroyed. One of 

 the difficulties was in locating hidden containers. 

 A few of these in a single block of houses were 

 sufficient to enable Aedes calopus to reach other 

 houses and decrease the efficiency of the work. 

 As the ordinance was not properly supported, it 

 became evident that the sanitary department 

 would be obliged to undertake the task of screen- 

 ing, and making inaccessible to mosquitoes, aU 

 water barrels, tanks, cisterns, wells, etc. This 



