454 AGEICULTXJEAL AND INDUSTRIAL BACTERIOLOGY 



has been transmitted from animals affected with inflamma- 

 tion of the udder (mastitis). 



Classification op Market Milk 



Methods of classifying market milk differ with the local- 

 ity. In a number of cities milk has been divided into four 

 grades: certified milk, inspected milk, pasteurized milk, 

 and uninspected milk. 



Certified Milk. — The term certified milk was introduced 

 originally to designate milk produced by a dairy which had 

 a regular system of inspection by some board of health or 

 committee of physicians. The requirements which must be 

 met when producing milk of this type are numerous and 

 must be rigidly adhered to, Among the more important 

 items are that the animals must be shown by continual 

 veterinary supervision to be free from contagious diseases. 

 The attendants, particularly the milkers, must be in good 

 health ; the stables must be sanitary, well lighted, free from 

 dust ; milking vessels must be sterile and every reasonable 

 precaution used to prevent bacteria getting into the milk. 

 When milk has been drawn from the animal, it must be 

 quickly cooled, sealed in bottles and kept cool until it has 

 been delivered. Furthermore, in most cases a bacterial 

 standard is imposed and certification is withdrawn if milk is 

 found consistently to have more than ten thousand bacteria 

 to the cubic centimeter. In a few instances milk can be 

 certified when the numbers do not reach more than twenty- 

 five thousand. Additional requirements over those of the 

 other grades of milk make it necessary to charge a higher 

 price for certified than for other types of milk. 



Inspected Milk. — Inspected milk is milk that comes 

 from a dairy where the cows have been inspected and cer- 

 tified to be free 'from tuberculosis. It must be drawn and 

 cared for under sanitary conditions, but the extreme pre- 

 cautions used in certified milk are not required. 



