1 70 CONTROL OF THE MILK-SUPPLY. 



they begin to develop with great rapidity. But if the milk is at once 

 reduced to a low temperature, the bacteria that have found their 

 way into the milk will not grow very rapidly. These facts are so 

 simple as hardly to require statement; but, unfortunately, many a 

 dairyman, although he may theoretically understand them, fails to 

 appreciate their importance. The essential point to be emphasized 

 is the necessity of immediately cooling the milk to a temperature as 

 low as 40 F. if possible. It is just as necessary to cool clean milk 

 as it is to cool dirty milk. Unless it is done, the cleanest milk will 

 soon contain as many bacteria as the dirtiest milk. 



Straining and Filtering. The long-continued practice of 

 straining the milk through a metal strainer or through cloth has in 

 its favor the fact that it will remove the larger particles of dirt; but 

 it does not remove the bacteria, for they will pass through any 

 strainer. Sand niters have also been used by some dairy com- 

 panies, and these are more efficient than simple straining. But 

 these niters are not of very much value and they are not widely 

 used. Centrifugal force is sometimes used for cleaning the milk, 

 and is fully as efficient as sand filtering. All of these means, while 

 effective in removing the large particles of dirt, are. practically of 

 no value in removing the bacteria, which show as high numbers 

 after such treatment as before. 



II. TRANSPORTATION PROBLEMS. 



Under this head will be included not only methods of treating 

 milk during transportation, but also of preparing it for preservation 

 during the transportation or until it is consumed. Milk, as a rule, 

 receives no preparation for transportation, except that of cooling and 

 placing in clean cans. Then, if rapidly shipped and kept cool, it 

 should remain good until some time after it has reached the con- 

 sumer. But the rapidity of bacteria growth, especially in hot 

 weather, makes it difficult to transport milk, in good condition, for 

 very long distances. Consequently, careful search has been made 

 for some method* of treating milk so as to preserve it. 



