56 DATA FOR MILK INSPECTION. 



posterous to assert that an article which is wholesome 

 when containing nine per cent, of non-fatty solids, be- 

 comes unwholesome when containing eight per cent. 



The unwholesomeness of milk arises not from change 

 in the proportions of its principal ingredients, but from 

 contamination with microorganisms. The danger from 

 certain specific organisms has been mentioned, but 

 the more frequent danger is from the ordinary non-pa- 

 thogenic or putrefactive microbes, which, unless special 

 care be taken, are invaribly present and multiply rapid- 

 ly. To prevent such conditions, resort is had to 

 sterilization by heat. Brief exposure to a temperature 

 of 2 1 2° F is sufficient in most cases, but if the milk be 

 subsequently exposed to air at ordinary temperatures, 

 or mixed with unboiled water, it will be again contam- 

 inated and undergo putrefactive changes. In the warm- 

 er seasons of the year, these changes occur with great 

 rapidity. Since clinical experience seems to show that 

 boiled milk is frequently an unsatisfactory food for in- 

 fants, methods of fractional sterilization at lower tem- 

 peratures have been suggested. These depend on 

 the fact, that, while spores and immature microbes 

 require a rather high temperature for their destruc- 

 tion, fully developed organisms are more easily kill- 

 ed. By heating the milk, therefore, to a temperature 

 much below the boiling point, the adult microbes are 

 killed, while the milk solids are not unfavorably affect- 

 ed. The spores and immature organisms will, however, 

 survive and may in a few hours develop, hence the 

 milk is again heated, as before, and these later devep- 



