MILK FROM COWS WHICH HAVE BEEN IN MILK 71 



duction of this bitter flavor in milk. Conn has described a 

 micrococcus which produces a bitter flavor, and Weigmann has 

 described a bacillus which produces a similar effect. Nearly 

 all of the investigators agree that the germs causing the bitter 

 flavors in milk belong to the group which acts upon the casein. 

 The bitter flavor is most commonly found in milk that has been 

 heated and then cooled to a low temperature. The heat destroys 

 the bacteria that produce lactic acid, but does not kill those that 

 produce the bitter flavor, owing to the fact that they are spore- 

 producing. 



The germs that produce a bitter flavor do not develop in 

 milk that is partly soured, because an acid reaction is unfavorable 

 to their growth. 



It was formerly thought that the organisms that cause the 

 bitter flavor in milk produced butyric acid. This theory, 

 however, has been largely overthrown, as it has been found that 

 these germs are chiefly of the kind which peptonize the casein 

 and produce gas. 



Milk from Cows which Have Been in Milk for a Long Period. 

 The difference in the composition of the fat yielded by cows in 

 different stages of the lactation period does not seem to affect 

 the quality of the milk to a noticeable extent. If the cows have 

 been giving milk an unusually long time, the milk may become 

 abnormal. 



The impurities in the small amount of milk yielded by a cow 

 almost dried up are quite apparent, and the causes of the presence 

 of these impurities are readily understood. The small amount of 

 milk drawn from such a cow would contain a proportionately 

 larger amount of dirt and germs than would a larger amount of 

 milk drawn from a cow yielding more milk, providing the cleanli- 

 ness of the udder and manner of milking were the same. Cows 

 giving a good quantity of milk always seem to have a cleaner 

 udder. This has been laid to the more vigorous circulation of the 

 blood in the udder of the cow that yields a larger portion of 

 milk. 



When cows calve once a year, and have a rest of about seven 

 weeks previous to parturition, if proper precautions are taken 



