1909] on the Americans and the Panama Canal. 705 



The sanitary work in the Canal Zone is remarkably carried out 

 in every detail. Take, for instance, the drainage. Open ditches are 

 used in order to concentrate surface waters where they can be kept 

 under control. These ditches are kept oiled by means of drip vessels, 

 and are kept free of vegetation and other obstructions that are 

 favourable to the propagation of mosquito life. Near the permanent 

 settlements many of the ditches have been lined and paved, and the 

 stone surfaced with cement mortar. Seepage waters sifting through 

 on hillsides and near the base of hills are carried olf by means of 

 tile drains. The banks of streams where anopheles are to be found 

 are kept clear of vegetation. Oil is kept dripping into these streams 

 so that it will collect in shallow places and prevent anopheles occur- 

 ring there. During the dry season the rivers and larger streams 

 become almost stagnant. They are then prolitic sources of auopheles- 

 breeding. Vegetable matter collecting in such places has to be con- 

 stantly removed, and the stagnant waters are kept covered with oil. 

 Narrow channels within the bed of the stream are dug in order to 

 keep the water in motion. Where anopheles larvae occur in moving 

 water, they are destroyed with poisonous substances such as phinotas 

 oil or carbolic acid. The reservoirs are kept stocked with tish. The 

 grass around the edges of the water sm'faces is cut down. Sulphate 

 of copper and constant sweeping keep the streams and ditches clear 

 of alga3. For larvacides, crude oil, carbolic acid, and phinotas oil 

 are used. Fish are useful as destroyers of larvse, providing there is 

 absence of vegetable scum and vegetable growth. 



Anopheles hide in the grass when there is a high wind. When 

 the jungle is removed where anopheles breed they look for the 

 nearest shelter. This accounts for the increase of mosquitoes in 

 houses immediately after the clearing is made. Along the edge of 

 the clearing mosquitoes are generally present, when they are not 

 noticed in the houses near the clearing. The sharpest watch is kept 

 in locating breeding places. The smallest pool of stagnant water is 

 not allow^ed to remain. So much so that the laws of the Zone pro- 

 hibit cattle and other animals being loose near settlements. Tliey 

 are allowed to pasture only on grounds specified as safe by the Sani- 

 tary Department, because they leave depressions with their hoofs in 

 the soft ground, and these depressions are apt to collect stagnant 

 water. 



When labourers' cars are moved from infected districts to camps, 

 they are fumigated before shipment in order to destroy all infected 

 anopheles. When anopheles become numei-ous near or in barrack 

 buildings fumigation is applied. Anopheles are more apt to be 

 found in barrack buildings than in American houses, as ignorant 

 labourers care little about mosquitoes and leave the doors wide open, 

 where it is possible to leave them open, as the Americans have every- 

 where applied self-closing devices on nearly each door. Sulphur is 

 found to be the most efficient substance used for fumigation. Where 



