BACTERIOLOGY OF MILK 



139 



scarlet fever and diphtheria, however, have been di- 

 rectly traced to contaminated milk. 



It is important to keep flies from milk. A fly can 

 readily infect milk through the filth which it carries on 

 its legs. 



Fig. 46. — Colonies of bacteria transplanted by a fly's feet 

 (Magruder). 



When properly supervised by the health authorities, 

 pasteurization of the milk offers the best protection 

 against all these various infections. In New York City 

 at the present time no milk, excepting that equal to 

 ^'certified" grade, may be sold unless it has been effectively 

 pasteurized. 



