Page:Popular Science Monthly Volume 73.djvu/177

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the same milk pail and mixing tank, some of the difficulties in establishing a just, arbitrary standard may be appreciated.

It is difficult to induce the public to realize that refined methods of analysis, the more careful attention to breeds and breeding, the great difficulty of supplying from considerable distances, the ever-increasing urban demand, the introduction of centrifugalization and other important considerations have entirely changed the complexion of the milk problem within a very recent period.

Many of us do not realize that much of the milk consumed in our large cities is taken from herds kept as far as 300 miles or more from the consumer, and when it is delivered to him is frequently forty-eight hours old. The problems surrounding the transportation of such milk in the summer season may be in part appreciated when we know that the presence of 5,000 bacteria to the cubic centimeter is considered a reasonably low count and that under favorable conditions this number is capable of doubling by geometrical progression every half hour.

Samples of commercial milk taken in New York city recently showed 35,200,000 bacteria to the cubic centimeter; London, 31,888,000; Washington, 22,134,000. That seventy-eight typhoid germs in one cubic centimeter of milk increased in seven days to 440,000,000 furnishes an illustration of the possibilities in this direction, and when one realizes that one cubic centimeter is equivalent to about sixteen drops, some idea may be gained of the bacterial population of much of the milk we drink.

Milk removed properly from a perfectly healthy cow, and kept in receptacles previously sterilized, contains practically no bacteria, and may at a low temperature be-preserved for days without material change. When, however, these precautions are not observed the results are as above indicated. Not all these germs are harmful, but many varieties are exceptionally prejudicial to the health of children. Each of 500 epidemics recently investigated, including typhoid fever, scarlet fever and diphtheria were found to be caused by contaminated milk. That 11 per cent, of milk samples examined from Washington contained tuberculosis germs need not be considered as exceptional and can be verified by the examination of data of a similar nature from other cities. And when we understand that the milk supply of New York city, for example, is derived from the product of 35,000 farms and shipped from 700 creameries located in six different states, it is easy to appreciate some of the difficulties surrounding the protection of the community from the sources of infection contained in milk.

In recent years the prominence given to tubercular disease in cattle, with the consequent appearance of the tuberculosis germ in the milk of such cattle, has entirely overshadowed the importance of certain other diseases in cows, likewise accompanied by the presence in the milk of cows so suffering of enormous numbers of bacteria character-