Page:Popular Science Monthly Volume 80.djvu/74

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THE POPULAR SCIENCE MONTHLY

being fought against poor milk in many instances with gratifying results. A reduction of infant mortality is usually noted when the public milk supply is improved. Laudable efforts are being made by health authorities in various cities in this country by introducing ordinances, forbidding the selling of milk derived from tuberculous cows, unless the milk is pasteurized. It will, however, require the intelligent and active support of consumers to make these efforts successful.

PSM V80 D074 Problem of city milk supply 5 1912.png

Photograph 5

Milk is secreted from the mammary glands in a sterile condition, that is to say, germs are totally absent. When the milk is discharged from the glands and enters into the cistern—the large reservoir—of the udder, some bacteria gain access; these having invaded the udder from the outside through the teat duct, a small canal in the teats through which the milk is withdrawn. The number of germs entering here is relatively small, however. The large numbers usually found in market milk enter during the process of milking and are the result of multiplication during transportation and storage, unless the milk is kept at a temperature below 40° F. No matter how careful the milker may be, some germs are bound to enter. It is therefore necessary to cool the milk rapidly after milking and keep it cold until consumed. We have then to consider chiefly two points in the production and handling of milk, first cleanliness in all manipulations and cleanliness of all utensils, and second rapid cooling and storage or transportation at low temperatures.

Milk is the natural food for all mammals and each species of mammal produces a milk of such composition as is most suitable for the young of the species. The-composition of cat's milk differs from that of