. Typhoid fever; its causation, transmission and prevention . ter use offiltration. St. Louis, Mo. The water-supply of St. Louis is takenfrom the Mississippi River, just below where the Missouri 244 TYPHOID FEVER, enters. The water is intensely muddy at times, and isnever clear. Mark Twain or some one else once said that TYPHOID MORBIDITYPER 100,000 TYPHOID MORTALITYPER 100,000 I I ilJ J 4 1Si s| - I i < « I il il J 1 ^ i I i_i si si il ;;: qI 2 s| ^ il ^ ^1 Fig. 37. Effect of Filtration in Reducing the Typhoid Fever Death-rates andthe General Mortality in a Suburb of Paris. (After Chabal.)
. Typhoid fever; its causation, transmission and prevention . ter use offiltration. St. Louis, Mo. The water-supply of St. Louis is takenfrom the Mississippi River, just below where the Missouri 244 TYPHOID FEVER, enters. The water is intensely muddy at times, and isnever clear. Mark Twain or some one else once said that TYPHOID MORBIDITYPER 100,000 TYPHOID MORTALITYPER 100,000 I I ilJ J 4 1Si s| - I i < « I il il J 1 ^ i I i_i si si il ;;: qI 2 s| ^ il ^ ^1 Fig. 37. Effect of Filtration in Reducing the Typhoid Fever Death-rates andthe General Mortality in a Suburb of Paris. (After Chabal.) when the wind blew over the water it raised a water is not filtered, but for many years has beenpassed through settling basins, where 8o or 90 per cent INFLUENCE OF PUBLIC WATER-SUPPLIES. 245 of the mud was removed. In 1904 this process of sedi-mentation was rendered somewhat more efficient byadding two chemicals to the water before it entered thebasins, namely, sulphate of iron (copperas) and lime. O r- ct <o ta ^ r^ 00 oi r- N W ^* 10 «o r^. ^XATION CHEMICALPRECIPITATION Fig. 38. Diagram Showing the Relation between the Water-supply and theTyphoid Death-rates in St. Louis, Mo. Since then the water in the city has been clearer andmore healthful, although the quality is still far from thatof the effluent of a good filter plant. The improvement in the water seems to have re- 246 TYPHOID FEVER. duced the typhoid death-rate, which had begun to increase after the opening of the Chicago Drainage Canal. Philadelphia, Pa. The water-supply of Philadelphia is taken from the Schuylkill and Delaware Rivers. 1000 ;8oo PHILADELPHIA, PA. DIAGRAM SHOWING THE POPULATION, NUMBEB, OF DEATHS FROM TYPHOID FEVER, AND THE TYPHOID DEATH RATES, BY YEARS. roo u_500
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