THE BACTERIOLOGIC EXAMINATION OF MILK 



Physical and chemical examinations of milk give information 

 about its richness and food value and the presence of preserva- 

 tives or adulterations. The commonest adulterant — water — may 

 leave the milk as wholesome as the natural product unless the 

 water is contaminated with disease germs, but the consumer is 

 paying for more than he is receiving. Chemical and physical 

 tests, therefore, are commercially necessary to protect the con- 

 sumer, but give no insight into the sanitary condition of the milk. 

 Bacteriologic examination is designed to determine the quality of 

 milk in relation to health. 



Bacterial examination is made for two purposes, namely, to 

 estimate the degree of cleanliness surrounding the production and 

 handhng of the milk, and to detect the presence of infectious 

 micro-organisms. The degree of cleanUness can be determined 

 within limits by simple enumeration of bacteria. The total count 

 gives valuable information about the conditions at the dairy, the 

 care practised , during milking operations, and the temperature 

 maintained during transportation. The count of bacteria, there- 

 fore, is of immense value to the health officer. 



The interpretation of bacterial numbers in milk is not as simple 

 a matter as might appear at first glance. The bacteria count 

 should be considered one of several tests, the results of which 

 give information as to the quaUty of the milk. Knowledge of 

 conditions surrounding the journey of milk from producer to con- 

 sumer should accompany and influence the final judgment. Milk 

 may have been produced with much care and the initial number of 

 bacteria may be small. But, if the milk is not promptly cooled 

 and kept cool up to the time of delivery to the consumer, bacteria 

 will multiply and the final product will give high counts. Further- 

 more, the sources of bacterial pollution are numerous, and mere 

 counts give only a limited insight into the exact source of con- 

 tamination. If large numbers of bacteria enter the milk at the 

 point of production, lack of care or cleanliness at one or several 

 points is indicated. The cows may be dirty; the stable air may 

 be rich in dust; the pails, cans, and other utensils may not have 

 been properly washed and steamed. It is not possible to deter- 

 mine, by merely enumerating Jpacteria, which part of the produc- 

 tion or handling is at fault. The producer may do everything 

 to the best of his knowledge. The only way to find the exact 



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