DAIRY INSPECTION 175 



milk is run through a machine known as a clarifier, in 

 which the milk is centrifugalized and the heavier sub- 

 stances, such as dirt particles, cells, and some of the bac- 

 teria, separated from it. The process is known as clari- 

 fication. When determined by the plate method, the 

 number of bacteria is frequently greater after clarifica- 

 tion than before, but this increase is probably due to the 

 breaking up of clumps of organisms by the centrif ugali- 

 zation. Some of the bacteria are removed from the milk 

 since the sludge or residue remaining in the clarifier 

 contains bacteria in considerable numbers. The per- 

 centage removed cannot be very great, however, because 

 the milk is exposed to the separating action for only a 

 short time. The sludge or residue is composed very 

 largely of the amorphous substances normally present in 

 milk, the remainder consisting of bacteria, cells, hair, and 

 particles of dirt. If clarified milk is subsequently centri- 

 fugalized for three minutes at 3000 revolutions per min- 

 ute, sediment will be deposited, showing that all of the 

 sediment is not removed by clarification. All gross sus- 

 pended dirt, such as hairs, dust particles, etc., are, how- 

 ever, removed by the clarifier, and for this purpose it has 

 many advantages over strainers. But milk containing 

 pathogenic organisms is no cleaner from a hygienic 

 standpoint after clarification than before (Bahlman, 

 Hammer). 



4. Feeding. The cows should not be fed immedi- 

 ately before milking. When hay or other dry fodder 

 is brought into the stable and distributed around among 

 the cows, more or less dust is liberated. This dust con- 

 tains numbers of bacteria, principally peptonizers, and 

 if milking is done while it is floating about in the stable 

 air some of these organisms will get into the milk. If 



