A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . ed on a polluted but deep water, alai-go river, for instance, the amount of bacterial purifi-cation amounts to over ninety per cent., commonlyover ninety-five per cent., anil a further element of 277 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. safety lies in the fact tliat storage in ice-houses duringthe months ehipsiug between tlie winter luirvest andtlie summer distribution tends still further to reduce thenumber of germs present in the ice cake. Be
A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . ed on a polluted but deep water, alai-go river, for instance, the amount of bacterial purifi-cation amounts to over ninety per cent., commonlyover ninety-five per cent., anil a further element of 277 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES. safety lies in the fact tliat storage in ice-houses duringthe months ehipsiug between tlie winter luirvest andtlie summer distribution tends still further to reduce thenumber of germs present in the ice cake. Be that as itmay, however, there is small e.\cuse for the too commonpractice of cutting ic(^ from grossly polluted waters, forwith even a high percentage of exclusion some germs doenter the ice, and it has licen shown that typhoid germsare at times capable of surviving a three mouths impris-onment therein. Touching upon this question of the ability of typhoidgerms to withstand freezing, the instance of the epidemicat Plymouth, Pa., is a case in point. There the dejectaof a patient lay frozen upon a hill>iiile from .lanuarv. Fig. .5031.—Chart showing Distribution of Clioleni , in the Epirtemic of1892, at Hamburpt ami Altona. ^—.Boundary between the two cities;• , cases of cholera : o, cases iuiporttd from Hamburg. until March, when tbey were washed by the meltingsnow into the city water system witli most disastrousresults. Stress should be laid upon the fact that the large per-centage of bacterial purification which results from freez- ing, as above referred to, is due to the mechanical exclu-sion of suspended particles by the growing crystals andnot to a mere lowering of temperature. Even the intensecold of liquid air is but iiulillerently germicidal. Beyond the ordinary wash caused by storms uponevery water-shed, some rivers are exposed to sudden andgreat concentration of pollution througli tlie sweepingaway of piles of tilth which accumulate ujion tlieir rockyfor
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