706 Mr. A. Henry Savage Landor [June 18, 



there is danger of harming fabrics and metals, snch as in the work- 

 shops, pyrethrum powder is used. Camphor pheniqne gives good 

 results, because its fumes produce no appreciable stain. It leaves a 

 faint odour of camphor, which prevents vermin from destroying 

 fumigated fabrics. 



When, after all this, surviving mosquitoes are detected anywhere, 

 they are killed by the most delightful of all, the squashing system. 

 A small square of metallic screening attached to a stick supplies an 

 effective instrument of destruction with the slapping process. Where 

 tents are used in temporary camps, a labourer is employed to go 

 through each tent several times a day, but especially in the morning, 

 to kill off all gorged mosquitoes. 



The method of preventing increase of malaria in Zone camps is 

 highly interesting. Each week the district physician makes a report 

 of the number of cases of malaria occurring in his district. The 

 report shows each section of his district and each group of houses 

 where the cases occurred. These reports are sent direct to the Chief 

 Sanitary Inspector, who notifies the District Inspector as to \yhich 

 section of .his district the malarial cases are coming from. A chart 

 is kept in each district by the District Inspector, which shows the 

 increase and decrease of malaria cases in his district each week. The 

 figures on this chart indicate the percentage of population that are 

 sent to the hospital with malaria. At any section of a district where 

 malaria increases, and where the rate remains abnormally high, the 

 Division Inspector investigates conditions and tries to determine the 

 cause or source of the increase of malaria. The cause of the increase 

 of malaria may be due to labourers coming from other infected areas, 

 exposure and other changes of surface topography which are necessary 

 in the course of the progress of the excavation work. Areas which 

 have been kept for eight or nine months with a relatively low 

 malarial rate have suddenly dropped to the bottom of the list, when 

 it has been necessary, for canal construction purposes, to block up 

 and change the natural drainage conditions that existed previously. 

 This makes the anti-malarial work in the Canal Zone much more 

 difficult than it Avould be elsewhere. The nature of the anti- 

 malarial work changes, and new breeding areas are continually brought 

 into existence as the work progresses. 



The last case of yellow fever occurred in the Canal Zone during 

 December 1905. There is a larger non-immune population in the Canal 

 Zone at the present time than there has ever been. In other words, 

 if a case of yellow fever occurred on the Isthmus to-day, the epidemic 

 that would follow would be exceedingly serious. In other tropical 

 localities subject to yellow^ fever, the non-immune population increases 

 and decreases from time to time. Yellow fever follows this increase 

 or decrease. On the Isthmus, the Department of Quarantine keeps 

 in touch with all yellow fever ports, and is constantly on the look-out 

 for the introduction of cases of yellow fever. When such cases occur 



