MICRO-ORGANISMS IN MILK 297 



but in carelessly managed dairies there would undoubtedly be a 

 greater difference. Clean cows with clean udders and teats pro- 

 duce a milk with small germ content even with wet milking. 'How- 

 ever, any condition that tends to increase the number of bacteria 

 should be eliminated as much as possible. 



Not of least importance is the sort of pail used to receive the 

 milk. Wooden pails are being rapidly replaced by metal ones, 

 because the latter are cheaper, more durable, and easier to clean. 

 Aside from the bacteria that are present in improperly cleaned 

 pails, the wide opening of the usual style admits much of the dirt 

 that drops from the cow during milking and dust from the air. 

 This fact was first recognized by the introduction of the so-called 

 "strainer pail." This is an ordinary metal pail of which one- 

 half or less is covered to protect the milk from dust falling into 



Fig. 102. Showing how a pail set on the level offers a larger space for dust to 

 enter than one held at an angle. 



it. The milk is strained by pouring it out of the pail through a 

 section of closely woven wire-cloth soldered into one side of the 

 can. This pail never was popular and is now practically aban- 

 doned. 



It is not difficult to realize that a great deal of dirt ordinarily 

 drops into the milk during the milking process, since much of 

 it is held by the foam that forms on the surface. As milking pro- 

 gresses the foam becomes darker with dirt particles. The germ 

 content of the foam, however, does not appear to be excessive, 

 according to Harding, Ruehle, Wilson, and Smith, who found in 

 a series of 36 samples that the foam had a germ content of 13,511 

 bacteria per cubic centimeter, while in the center of the milk there 

 were 14,876 bacteria per cubic centimeter, and in the stirred milk 

 18,089. These figures suggest that the dirt particles in the foam 



