The Campaign in Havana 237 



occupied while looking for employment. It is the 

 custom in Havana for clerks and employees to live 

 and sleep in the stores or establishments where 

 they are employed. This arrangement helped 

 to make a concentration of non-immunes, and 

 hence the yeUow fever cases in the locality men- 

 tioned. 



In the preliminary mosquito destruction cam- 

 paign one inspector and two oilers were employed 

 to visit all houses and yards, and to destroy all 

 mosquito-producing containers. The length of 

 time necessary for the thorough inspection of the 

 district above mentioned was soon determined, and 

 it was then divided into sections, of such sizes that 

 one inspector and two oilers could destroy or con- 

 trol any mosquito breeding places in every house 

 and yard in their section once a week. Later this 

 system was extended throughout the entire city, 

 which was divided into thirty districts. The first 

 inspection of the city showed a total of 26,000 

 water containers with mosquito larvae. Most of 

 these were producing Aedes calopus, which were 

 very numero\is in the residences. 



The method of procedure was as follows: A 

 list of all houses was kept at the main office. The 

 district inspectors turned in each day a report 

 of containers found, and an entry was made on 



