MALARIA 109 



Camphor and carbolic acid can be used, equal parts, 4 ounces dis- 

 solved bv gentle heat, per 1,000 cub. ft. Only about half an hour is 

 required. 



(3) By natural enemies, e.g., bats, birds, lizards, dragon flies, 

 fishes as Girardinus poeciloides (millions), tadpoles. All such should 

 be bred and protected. Such means, however, are not always best. 



1 1 mav be much cheaper and better to remove the water altogether 

 than to maintain " natural enemies." 



(4) Dealing with the larvae. — All small receptacles for water should 

 be removed or filled with lime or given a surface film of kerosene, if 

 such are used for table legs to keep away ants, &c. 



Larger quantities of water and small streams can be covered with 

 a thin surface film of crude kerosene which does not permit the larvae 

 to reach the surface for air. It requires half an ounce per square yard 

 ever}' seven days to be effective. 



Wherever possible destroy and do not treat mosquito breeding 

 places. Small pools should certainly be drained. Holes in rocks and 

 trees should be filled with rubble and cement. Plants which breed 

 them, as pineapples, bananas, &c., should be removed from near dwell- 

 ings. Culicines breed in palm trees and sugar cane. Larvicides, 

 such as copper sulphate, &c., can be used in water, which rapidly kills 

 ofT the larvae, but it becomes poisonous for other animals. 



(5) Screening of breeding places is sometimes necessary, such as 

 of water tubs, wells, cesspits, &c. Cattle should be watered at certain 

 parts only and the hoof impressions levelled. 



(6) Drainage. — Open channels should be cut in the soil and con- 

 creted. Drains could be of stone and gravel. Local material available 

 will help one to decide. The subsoil should be drained by pipes. As 

 much as possible of the surrounding land should be suitably cultivated. 



(7) Trees and bush. — Eucalyptus trees are not worth while. Many 

 .trees should not be allowed to remain near to houses as they attract 



and give out moisture, exclude breeze and increase heat. 



All bush and undergrowth Avithin 200 yards of all villages, houses 

 and dwellings and all grass within this area above 12 inches in height 

 should be cut down. A mosquito will not be able to cross such a zone 

 without destruction by sun or wind. 



(8) Houses should be built several feet above the ground, upon 

 sites high and dry, well away from coolie lines and native villages. 

 Houses should be lofty — of stone, if possible, or brick — with good light 

 and ventilation, which mosquitoes do not like. Whitened walls are 

 good. Curtains and fancy decorations are bad. 



As to the height of the site, one may remember that the temperature 

 of the air tends to fall 1° F. every 300 feet above sea-level. Malaria 



