Contamination of Milk. 53 



grosser particles of contamination after entrance. In 

 the case of straining, the method is usually applied at 

 the time of milking, but in the case of filtering and clar- 

 ifying, it is carried out at the milk station, in an effort 

 to improve the appearance of milk and overcome the in- 

 fluence of careless methods of the producer. By the use 

 of strainers, either metallic or cloth, it is possible to re- 

 move particles of hair, undissolved dirt and manure, but 

 it must be remembered that these grosser visible par- 

 ticles of pollution are not really the cause of the troubles 

 which may ensue in improperly handled milk. The bac- 

 teria which are adherent to these foreign particles are in 

 large measure washed off in the process of straining, and 

 pass through the meshes of the finest strainer. The main 

 service, therefore, of straining is to improve the appear- 

 ance of the milk, and it has no effect on the quality in 

 any way. 



Production of clean milk. The problem of clean milk 

 is important, whatever may be the use to which milk may 

 be put. It is important in the manufacture of butter, 

 but owing to the fact that the fat is not readily acted 

 upon by bacteria, it is not so sensitive to bacterial con- 

 ditions, as when the milk is made into cheese. In this 

 product, the bacterial condition of the milk is a matter 

 of prime importance. In milk destined for direct con- 

 sumption, the exclusion of the bacteria becomes yet more 

 important. "While it is impossible to exclude bacteria 

 so completely that milk will not undergo fermentative 

 changes, yet for domestic consumption it is preferable 

 to have milk with as low bacterial content as can readily 

 be secured. The highest type of market milk, that known 

 as sanitary, or certified, is produced under such ex- 

 treme conditions of care as to contain the minimum germ 



