60 MILK [v 



cows which have been long milked often shows this 

 property. It arises from the fact that the original 

 condition of the nitrogenous matter in the milk be- 

 comes changed in an extraordinary manner, and a 

 large proportion of the fatty globules become free. 

 It has also been noticed that such milk contains less 

 calcium phosphate than normal milk. 



Means of preventing Changes in Milk. It may 

 be asked, How may these changes be prevented or 

 retarded ? Now, in doing so, the great agent is heat. 

 Cleanliness is not a less valuable instrument : clean- 

 liness in every way on the hands of the milker, on 

 the teats of the cow, in the milk-pails and other 

 receptacles used for holding the milk, in the byre, 

 etc. Immediately after milking, the milk should be 

 cooled down : the lower the temperature the better. 

 On the other hand, it may be sterilised by heating ; 

 and, in order to avoid imparting the disagreeable 

 boiled flavour to the milk, this may be effected by 

 heating it to 70 to 80 C. (158 to 177 Fahr.). The 

 addition of chemicals, so-called " preservatives," 

 cannot be too strongly condemned. Even such 

 comparatively harmless preservatives as bicarbonate 

 of soda, boracic acid, salicylic acid, and peroxide of 

 hydrogen, ought not to be used. 



The methods of sterilising milk and the import- 

 ance of cleanliness will be further referred to at the 

 conclusion of next Chapter on the bacteria of milk, 



