INTRODUCTION 



A PURE milk supply has ever been a 

 recognized desideratum, and the best 

 efforts of sanitarians and public offi- 

 cials have for many years been devoted 

 toward its attainment. The universal use 

 of milk as a food, and the important place it 

 holds in the diet of the world, have justified 

 every effort toward rendering it available 

 and wholesome for human consumption. 

 Heretofore, the insistence on a proper nutri- 

 tive value and the prohibition of the use of 

 preservatives have been the principal objects 

 sought, but with the development of the 

 science of bacteria, there has arisen a new 

 and a most important consideration concern- 

 ing milk. Good milk can no longer be de- 

 cided on the ground that it contains a re- 

 quired percentage of solids and is free from 

 deleterious chemicals, but it must also be 

 subject to the test of bacterial contamina- 

 tion. Since bacterial contamination may re- 

 sult in the conveyance of infectious diseases, 



such as typhoid, diphtheria, scarlet fever, 



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