CLARIFICATION OF MILK. 



185 



The Dirt in Slime. 



By dirt is meant those extraneous substances which find their way into 

 milk from without, or after the milk has left the udder. All milks, whether 

 certified or ordinary market milk, contain some dirt. It appears, however, 

 in different quantities in different milks, and the amount present in a gen- 

 eral way corresponds closely to the grade of the milk. 



An analysis of the dirt found in or gaining entrance to milk has resulted 

 in the recognition of definite substances associated with the cow, stable, 

 milker or utensils. Some of the materials are feces, dust, hairs, straw, 

 hay, epithelial cells, — in short any loose material on the cow or easily 

 detached from the cow, the milker, the stall; substances floating in the 

 air as the result of stirring hay or bedding or any dusty articles in the 

 stable; material adherent to the pail; and other foreign matter reaching 

 the milk through flies, straining, etc. 



In this particular connection our interests center in what the clarifier 

 may do toward undoing what has been done in milking and handling milk. 

 During the process of milking, as a rule, the dirt is added; then an effort 

 is made to remove it by straining and render it harmless by pasteuriza- 

 tion. The clarifier is now added as a means to assist in the removal of 

 dirt. 



It is evident that the clarifier as a centrifuge cannot remove that portion 

 of the dirt which goes into solution. No centrifuge can do this as long as 

 the solution diffuses throughout the whole mass; accordingly, this should 

 not be charged against the machine, because it is beyond the reach of 

 any present practical device, mechanical or otherwise. 



