Contamination of Milk. ^ 25 



the teat the bacteria make their way up into the milk 

 cistern and to a less extent into the milk ducts, and 

 e\en to the secreting tissue proper. Many forms un- 

 doubtedly enter but only a few are able to grow to any 

 extent. They are harmless guests and cause the cow no 

 trouble. They are found in the milk when it is drawn, 

 usually several hundred in every cubic centimeter. 

 Since the bacteria enter the udder through the teat, one 

 should expect to find the greater number in the lower 

 part of the udder, where they would be washed out dur- 

 ing the first part of the milking. As a rule the first 

 streams from each teat contain a larger number of or- 

 ganisms than those subsequently drawn. 



This source of contamination can not be wholly 

 avoided. Material reduction in numbers may be pro- 

 duced by excluding the fore-milk i. e., the first few 

 streams drawn from each teat. Such milk should be 

 drawn into a separate container, not milked on to the 

 floor. It may be used for feed. It is always low in bat- 

 ter fat. While such a method will reduce the number 

 of bacteria in the milk slightly, it has no particular 

 effect upon the keeping quality of the milk since the or- 

 ganisms found in the udder grow very slowly at ordi- 

 nary temperatures and produce no marked changes in 

 the milk. 



Some times the udder is invaded by harmful kinds of 

 bacteria which grow rapidly and cause an inflammation 

 of the gland, which diseased condition is known as gar- 

 get. See p. 144. 



Contamination from the animal. Milking is almost 

 always carried on under conditions, that must be called 

 unclean when it is considered that human food is being 

 prepared. Conditions are tolerated in the barn that 



