248 PESTS AND NUISANCES 



side drains; pots, kettles, tubs, springs, barrels of water, and 

 other back-yard collections should be drained, filled with earth, or 

 emptied. 



Running streams should have their margins carefully cleaned 

 and covered with gravel to prevent weeds and grass at the water's 

 edge. 



Lily ponds and fountain pools should, if possible, be abolished; 

 if not, the margins should be cemented or carefully graveled, a good 

 stock of minnows put in the water, and green slime (algae) regularly 

 cleaned out, as it collects. 



Where tanks, cisterns, wells, or springs must be had to supply water, 

 the openings to them should be closely covered with wire gauze (gal- 

 vanized to prevent rusting), not the smallest aperture being left. 



When neither drainage nor covering is practicable, the surface of 

 the standing water should be covered with a film of light fuel oil (or 

 kerosene) which chokes and kills the larvae. The oil may be poured on 

 with a can or from a sprinkler. It will spread itself. One ounce of 

 oil is sufficient to cover fifteen square feet of water. The oil should 

 be renewed once a week during warm weather. 



Particular attention should be paid to cesspools. These pools, when 

 uncovered, breed mosquitoes in vast numbers; if not tightly closed 

 by a cemented top, or by wire gauze, they should be treated once a 

 week with an excess of kerosene or light fuel oil. 



Certain simple precautions suffice to protect persons living in mala- 

 rial districts from infection : 



First : Proper screening of the house to prevent the entrance 

 of the mosquitoes (after careful search for and destruction of all 

 those already present in the house), and screening of the bed at 

 night. The chief danger of infection is at night (the anopheles 

 bite mostly at this time). 



Second : The screening of persons in malarial districts who 

 are suffering from malarial fever, so that mosquitoes may not bite 

 them and thus become infected. 



Third : The administration of quinine in full doses to malarial 

 patients to destroy the malarial organisms in the blood. 



Fourth : The destruction of mosquitoes by one or more of the 

 methods already described. 

 These measures, if properly carried out, will greatly restrict the 



