. Public health manual . e of plenty of organicfood for them. Organic pollution and high bacterialcontent go hand in hand. The presence of the hacillus coU communis type ofbacteria in a sample is indicative of the character ofthe pollution. These organisms have as their naturalhabitat the intestinal tracts of man and of warm-bloodedanimals. It is impossible to differentiate betweenB. coli of animal and human origin, and the positiveresults should not be interpreted as indicat-ing pollution from human sources. WATEE EXAMTNATIONS 205 The laboratory evidences, derived from the result
. Public health manual . e of plenty of organicfood for them. Organic pollution and high bacterialcontent go hand in hand. The presence of the hacillus coU communis type ofbacteria in a sample is indicative of the character ofthe pollution. These organisms have as their naturalhabitat the intestinal tracts of man and of warm-bloodedanimals. It is impossible to differentiate betweenB. coli of animal and human origin, and the positiveresults should not be interpreted as indicat-ing pollution from human sources. WATEE EXAMTNATIONS 205 The laboratory evidences, derived from the results ofour examination, merely indicate the presence or absenceof pollution. They are only of an indirect value in theinvestigation of typhoid infections and should not be re-lied upon as the only method of investigation of thecausation of cases of this disease. This is particularlytrue ji cases in which well waters are frequently sus-pected of having a causative relation to the disease. A(tMii of etuiA Oriyln.^ ?toj^Ke*.. O^intU. -tt/r-yct^^. There is but little evidence that well waters are com-monly responsible for typhoid outbreaks. The commonsources of pollution reaching wells, are from surfacewash and percolation through the soil. The possibilities of such pollution from surface washcan be ascertained by inspection. Many excavated wells 206 PUBLIC HEALTH MANUAL are subject to pollution from surface wash throughleaky walls and platforms, and much of this pollutionis usually from animal sources. This pollution can beprevented by making the walls of water-tight materialsuch as concrete, for about six feet below the surfaceof the ground, and extending the wall about a foot anda half above the general surface. Filling around thiswall with earth will form a mound to divert surfacewattr, and what surface water does reach the wellwill first have to percolate through at least six feet ofsoil, thus giving an opportunity for soil filtration, whichis an efficient method of purification.
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