MICRO-ORGANISMS IN MILK 285 



by Harding, Ruehle, Wilson, and Smith. These authors found in 

 a series of experiments that the germ content in milk from clean 

 udders the hair of which was clipped was greater than in milk 

 from undipped udders. The difference was not great, but the 

 authors think that clipping offers no distinct advantage. They 

 explain this rather surprising result by the assumption that after 

 clipping there is small protection against dirt, and bits of dead 

 skin that are constantly breaking loose fall with their share of 

 germs into the milk. 



Periodic grooming of cows will remove much dirt and loose 

 hair. Hairs are not infrequently found in milk and may carry 

 many bacteria. This is illustrated in Fig. 92, taken from Russell 

 and Hastings' Dairy Bacteriology, which shows the colonies grown 

 from a hair placed on an agar plate. 



Fig. 92. — Bacterfa on hair.s. Each colony on the hair represents one or 

 more bacteria that were adherent to the hair when it was placed on the sur- 

 face of the solid culture-medium (Russell and Hastings). 



During the winter, when cows spend most of the time in a 

 stable, the accumulation of dirt on the animal is usually greater 

 than during the summer. The same condition obtains during 

 the night, when cows are stabled. The morning's milk, there- 

 fore, as a rule, has a greater germ content than the evening's 

 milk. On the other hand, the fecal discharges are usually softer 

 in summer than in winter. Soft feces are more apt to splatter 

 into the milk than hard ones and adhere more readily to the skin 

 and hairs of the animal. Fodder rich in nitrogenous material is 

 also conducive to the formation of soft feces. 



In some dairies vacuum cleaners are used for currying cows. 

 Theoretically this is an ideal method, since the dirt is removed 

 from the stable without vitiating the air. However, experiments 



