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 centrifugali- 
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 
