. A practical study of malaria. ipal cause of must study the point by careful search for anopheleslarvae; and may often find that a small, unobserved pool in thestreet is more dangerous than a marsh a mile away. The number and nature of the breeding pools depend somuch upon the configuration of the ground, the character ofthe soil, and the amount of the rainfall that it is impossible togive very minute directions regarding the method of dealingwith them. The superintendent must be guided by his ownjudgment, remembering only the maxim, which applies to mostkinds of work, The simplest
. A practical study of malaria. ipal cause of must study the point by careful search for anopheleslarvae; and may often find that a small, unobserved pool in thestreet is more dangerous than a marsh a mile away. The number and nature of the breeding pools depend somuch upon the configuration of the ground, the character ofthe soil, and the amount of the rainfall that it is impossible togive very minute directions regarding the method of dealingwith them. The superintendent must be guided by his ownjudgment, remembering only the maxim, which applies to mostkinds of work, The simplest measures first. The height of the ground water is very intimately associatedwith the prevalence of malaria, since the quantity of surfacewater depends largely upon the height of the ground water, andthe latter, when appearing upon the surface, is a favoritebreeding site for malarial mosquitoes. Hence, measuresdirected toward the lowering of the ground water are of thehighest efficacy in the prophylaxis of malaria. This is evi-. Fig. 93.—Breeding pools on a rice farm. PROPHYLAXIS 309 denced by the results of the tiling of land and by the forma-tion of drainage districts for the reclamation of swamp procedures often render unnecessary the expenditure oflabor or money for the removal of breeding pools or other anti-larval steps. Ground water is lowered by various methods, the mostprimitive of which is ditching. These ditches are left openor are partly filled with gravel or stone, then with earth. Theunglazed tile drain is very effective; perforated drains havebeen employed also. In certain regions where the hardpan or impervious stratumis responsible for a high-ground water excellent results havebeen obtained by boring through this, thereby allowing thewater to escape into the permeable earth beneath. These arethe so-called absorbing wells. It is well known that rice culture increases the malaria of aregion to a great extent (Fig. 93). In some of the Orientalcountrie
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmalaria, bookyear1909
