410 MILK 



cause of trouble is to test the milk at all stages of handling, a time- 

 consuming and expensive process. It follows that any single test 

 is inadequate to afford proper control of milk-supplies. High 

 numbers of bacteria indicate that something is not as it ought 

 to be, and it is then the duty of the dairy inspector to follow 

 the trail and find the true cause of pollution. After locating the 

 source of the trouble the inspector should inform the producer 

 or dealer and suggest means for improvement. Repeated bac- 

 terial -tests will then show whether the trouble has been success- 

 fully dealt with. Large initial numbers mean that through care- 

 lessness or ignorance dirt chiefly cow manure has entered the 

 milk, a matter which is -not a pleasant consideration, to say the 

 least. If, however, large numbers of bacteria are due to multi- 

 plication during transportation the matter stands out in a dif- 

 ferent light. It is known that lactic acid bacteria, as a rule, 

 multiply in milk with greater rapidity than other bacteria. Con- 

 sequently, large numbers due to faulty temperature conditions 

 during transportation mean that the milk contains large numbers 

 of harmless lactic acid bacteria and not necessarily dirt. If 

 multiplication of lactic acid bacteria is permitted to continue until 

 several hundred million are present, a product is formed which is 

 distinguished from buttermilk only by the larger amount of fat 

 present. And buttermilk, in spite of many millions of bacteria, 

 is not considered either dirty or harmful. In this case, however, 

 the great majority of bacteria is of a known type, known to be 

 harmless, and not a mixture of many types among which there 

 might be pathogenic bacteria. Therefore a separate enumeration 

 of lactic acid bacteria is of distinct value. However, it should 

 be remembered in this connection that if the temperature during 

 transportation is high pathogenic bacteria may multiply to some 

 extent along with lactic acid bacteria, and the danger is propor- 

 tionately increased. Pathogenic bacteria are restrained or de- 

 stroyed only when the acidity is so high that the milk has a de- 

 cidedly sour taste, and in this condition milk is not marketable. 

 The consumer wants and pays for sweet fresh milk, not for milk 

 that is fermented and that may contain injurious micro-organ- 

 isms. 



More important for a sanitary survey of a milk-supply than 

 cleanliness of the product is the possibility of its carrying infec- 

 tion. At the present stage of our knowledge it is a difficult task 

 to isolate pathogenic bacteria from milk, because some do not 

 multiply in milk, and if it is kept cold practically none do. How- 

 ever, they may remain alive long enough to possibly cause infec- 

 tion, while other bacteria actually multiply. 



A further difficulty in finding infectiousness in milk is the fact 



