Page:Popular Science Monthly Volume 55.djvu/658

 distribution through the milk supply, it would appear that such a method is perhaps satisfactory.

So far as can be determined, this method is efficient in destroying pathogenic bacteria. Its efficiency is of course dependent upon the length of time that the milk is retained at the high temperature, and this can be regulated by the rate of the flow of the milk through the machine. All evidence we have seems to point to the conclusion that a temperature of 75° C, continued for a few minutes only, so far destroys or weakens the pathogenic bacteria which are liable to be found in milk that they need not subsequently be feared as producing disease. Of course, there are pathogenic bacteria that are not destroyed by this temperature, but they are not likely to occur in milk. The germs of typhoid, diphtheria, and tuberculosis are probably rendered harmless by such treatment, and these are the chief pathogenic bacteria of milk. Moreover, the other bacteria are very greatly decreased in numbers, so that the dangers of intestinal troubles are at least much reduced. In hospitals where Pasteurization has been adopted the results are as favorable as with sterilization.

The great value of this plan is, however, that it is practical on a large scale. In Copenhagen it has been in practice for some three years very extensively. In Denmark the amount of tuberculosis among cows is very great, somewhat more than half the animals suffering from this disease. As a result the public milk supply is regarded with more suspicion than in countries where the disease is less. It is everywhere recommended that the milk be always boiled before using, but the bother of treating the milk thus daily makes people unwilling to do it, and it is doubtful whether the practice is as common as the physicians think necessary. Some three years ago a company was organized to meet the public demand for safe milk, and it has adopted plans by which it furnishes Pasteurized milk on a scale as extensive as that of the ordinary milk-supply companies. The company has devised and manufactured two large machines which receive the milk. Pasteurize it, and cool it in a constant stream, and are capable of treating two thousand quarts an hour. The milk received by the company is tested chemically and filtered, and then allowed to pass through one of these large machines. After this it is placed in glass bottles and sealed with the company's seal. The heating is done by steam, and the cooling by brine cooled by an ammonia cooling machine. The greatest care is taken in cleaning and sterilizing the bottles, an enormous chamber some twenty feet long and six feet in diameter being used for a sterilizer. Into this the washed bottles are placed, the chamber hermetically closed, and then superheated