Bacteria in the Air 361 



beings and of domestic animals increase the germ con- 

 tent of the atmosphere of barns and stables. Germ-free, 

 or nearly germ-free milk can be secured more readily 

 by milking the cows in the open. The milk drawn in the 

 barn is almost always contaminated. 



These facts are extremely instructive in showing, not 

 only that the number of germs that may fall into the 

 open milk pail or into the open can may be very large, 

 but that they may prove of considerable significance in 

 determining the keeping quality of the milk. It follows, 

 therefore, that clean floors, clean walls, clean ceilings, 

 and clean cows are essential for a small proportion of 

 dirt and bacteria in the air in the barn. The cows should 

 not be brushed or fed shortly before milking, nor should 

 the barns be swept and bedding placed in the stalls at 

 that time. Intelligent precaution thus taken will well 

 repay the dairyman and will enable him to keep his milk 

 sweet and pure for a longer time. Many thousands of 

 bacteria that would otherwise fall into the milk pails 

 and into the milk can, while the milk is being strained, 

 may thus be kept out and undesirable decompositions 

 and flavors excluded. Much of the subsequent value of 

 the milk will depend on the proper observance of these 

 precautions, for, once in the milk, the bacteria will mul- 

 tiply there very rapidly when the temperature is at all 

 favorable. 



Bacteria on the cow's body. Many of the germs 

 found in freshly drawn milk are derived from the cow's 

 body. Minute particles of dried manure or bedding, 

 hairs, and scales from the skin, as they fall into the milk 

 pail, may each contribute various numbers and kinds 



