Milk is often unwholesome because it is obtained from cows that are not healthy. The commonest cause of its contamination is disease of the udders, but even disease in distant organs makes it undesirable. Milk taken from a sick cow should not be used for food. Unfortunately, chronic maladies like tuberculosis may exist in an animal for a considerable time without causing sufficient change to attract the keeper's attention. Tuberculosis of the udder or slight inflammation due to pyogenic microbes may easily be overlooked. Of 186 samples of milk, Dr. Eastes1 found tubercle bacilli in 11 and pus organisms in 47. Milk is often contaminated by dirt, which comes from the cows when they are not properly cleansed before milking, from the hands or clothes of the milker, or from the dust of the stable, barnyard, and milk room. Besides dirt, micro-organisms of various kinds gain access to it in this way. Some are innocuous, a few produce souring, and others are specifically pathogenic. Of the last, the commonest are the microbes of typhoid fever and diphtheria; and, possibly, of scarlatina and, in certain countries, of cholera. The typhoid and cholera germs are added to the milk with water used in cleansing the vessels in which the milk is gathered or kept, or added as an adulterant. They are also sometimes carried on the feet and proboscis of flies which convey them from sewerage to the home or dairy. They both grow freely in milk when it is kept sufficiently warm. Local epidemics of typhoid fever have frequently been traced to milk thus contaminated. Scarlet fever has been said to be communicated by milk when cows were milked by one who was recovering from the malady and who had not yet completely shed the skin of his hands.

In a report upon milk examination made by de Schweinitz, of Washington, to the Department of Agriculture, attention is called to the fact "that in the milk supply of our large cities the number of bacteria per cubic centimeter has been found to vary from 30,000 to 85,000, and has often been found as high as the number of bacteria in the sewage of several towns - namely, between 1,000,000 and 4,000,000 per cubic centimeter." Butler, a German authority upon the subject, claims that the maximum limit for milk that is fit for food is 50,000 germs in a cubic centimeter. If this rule is applied to samples obtained by de Schweinitz from 32 Washington dealers, the milk supply of only 13 was fit for use. Of the samples from these dealers, one showed only about 4000 bacteria in a cubic centimeter; one, 2500; five others, from 10,000 to 15,000; six, from 30,000 to 50,000; and the remainder, more than 50,000; in several instances, more than 100,000. De Schweinitz also examined 135 samples of milk obtained from a dairy in which the utmost pains were taken to prevent contamination. In a majority of these samples from 200 to 5000 bacteria in a cubic centimeter were found. Three samples showed more than 50,000, one more than 15,000 and less than 20,000; two more than 10,000 and less than 15,000; two more than 5000 and less than 10,000. These results show what can be accomplished by due care. Legal standards, both chemical and bacteriologic, have been established by certain health boards in the United States and other countries. The milk supply of communities thus safeguarded has consequently been greatly improved and made more uniform.

1 "British Medical Journal," November 11, 1899.

All this emphasizes the need of the utmost care in the handling of milk to insure its purity. Purity is the more necessary as milk is so largely used uncooked.

At the Clover Farm Dairy, which offers a particularly uniform rich and pure milk for use in Chicago, the following precautions are taken:

The herd is made up of grade Holsteins, grade Jerseys, and grade Durhams. These crosses are thought to give animals more vitality, better constitutions, and less liability to disease than the registered animals of the various breeds possess. It is also important, in the production of milk for baby and invalid food, to secure milk that retains its cream as well as possible. The cream of Jersey milk rises so rapidly that a thick buttery cream is produced that does not mix so readily with the milk after it has once risen as does that of most of the other breeds and their grades. This characteristic of the Jerseys adds to their value as butter cows, but detracts from their usefulness when a milk is wanted to retain its fat. Milk should be constantly agitated during the cooling process, for this prevents the rising of the cream until after it is cooled, and by this treatment cream and milk are much more readily and thoroughly incorporated when preparing it for feeding.

Each cow is tested for tuberculosis at frequents intervals, and also to determine her value as a butter producer. A cow not in perfect health cannot reach a high productive standard. These tests insure a healthy herd from which the milk is obtained.

The stable has cement floors and cement mangers. It is furnished with individual stalls. The stall work is of iron and woven wire. It has a good system of ventilation and has plenty of light.

The cement floors can be easily cleaned, and every day they are thoroughly flushed and scrubbed, abundance of water being at hand. A complete system of sewerage is provided.

One-half hour before milking, the cows are groomed. The milkers are required to cleanse their hands and put on white milking suits. One man is required to cleanse the udders of the cows just in advance of milking, using a sponge and warm water for this purpose. Each milk pail is furnished with a closely fitting strainer cover, into which is fastened a layer of absorbent cotton, so that all the milk passes through this cotton before entering the milk pail. The milk is poured out through a covered spout, and the strainer is not removed from the pail until the milking is finished, when it is destroyed and a new one is prepared for the next milking. The milk pails, strainers, cans, and all other utensils, also the bottles in which the, milk is shipped to the consumer, are thoroughly cleansed and then sterilized by live steam in a sealed room, the temperature of which is held at 212° F., for thirty minutes. The first milk from each teat is rejected, as experience has shown that germs which may sour the milk invade the milk-ducts and cannot be gotten rid of by washing alone.

As soon as the milk is obtained it is run through a centrifugal machine, such as has been in use for some years in creameries, as a means of rapidly and economically separating the cream from the milk. By its use the percentage of fat can be kept constant, and at the same time dirt or other solid matter that may have gotten into the milk in spite of the precautions previously used can be removed from it. Although in this operation the cream and milk are separated from each other, they are again mixed when they come from the separator, and there is left behind in the machine a peculiar mass of mucus, germs, etc., which it is very desirable to have out of the milk. Immediately after leaving the separator the milk is cooled to a low temperature. The milk is then bottled, each bottle stopped with a wood-pulp stopper, and a metal cap and a seal put over the top in such a manner that the contained milk cannot be reached unless the seal is destroyed. On each seal is stamped the date of the bottling. This seal is a guarantee of genuineness to the consumer. Although this process seems complex, it is in reality carried out quite readily by trained workmen.

The dairies which supply the Walker-Gordon Milk Laboratories in various cities are managed in much the same way, and an equally uniform and pure production is the result.

In several cities of the United States the whole or a part of the milk-supply has been taken under the voluntary supervision of medical societies cooperating with reputable dairymen. The societies appoint veterinarians, bacteriologists, and chemists. They fix and announce their requirements, and these are specified in contracts. Every month, at times not previously announced, samples of milk are procured and examined, and the veterinarian visits the dairy farm. If the milk examined comes up to the standard, a certificate is given; if not, the certificate is withheld until another examination shows the milk to be right. Inside of the metal cap on every bottle is a small certificate, printed and signed with the printed autograph of the Commission, stating that an examination was made on such and such a date, and that another will be made within the month and new certificates issued, and counseling buyers to watch for the change in dates.

Sterilization And Pasteurization

Pathogenic organisms in milk can be killed by boiling it. This constitutes sterilization. It is, however, then changed in taste and made distinctly less digestible. If milk is kept at a temperature of 700 C. (1580 F.), for twenty or thirty minutes, most of the germs will be killed. Their spores will not be destroyed but their growth will be checked for a time. This process is called Pasteurization. It does not modify the taste of the milk, nor lessen digestibility so much as sterilization does. Except in the hottest summer weather, resort to Pasteurization is not necessary to prevent the souring of milk. Pathogenic organisms should be excluded by scrupulous care in the collection and distribution of milk.