CHAPTER VII. 



MICROSCOPIC TESTS OF MILK. 



Mammitis in the cow. Cows very frequently suffer from 

 mammitis associated with the presence of streptococci. The 

 majority of dairies contain cows that show active inflammatory 

 changes in one or more quarters of the udder. The abnormal 

 product of such an udder always contains pus cells and strep- 

 tococci. Clinical manifestations of the disease vary from the 

 case exhibiting marked swelling of the udder, with a marked 

 abnormal secretion, down through various gradations of clinical 

 manifestations as exhibited through the condition of the udder 

 or secretion, to the normal (34). More than this, bacteri- 

 ological study of some apparently healthy udders reveals 

 streptococci in the whole organ or in particular quarters of the 

 udder. Sometimes in these cases'a history of a previous attack 

 of mammitis may be established by inquiry or by the discovery 

 of indurated portions of the udder by palpation, and other 

 times not. 



Tests for cellular content of milk. The development of 

 microscopic tests of milk has been actuated by a desire to 

 determine quickly which cows supplying city milk are suffer- 

 ing from garget and yielding pus cells and the accompanying 

 organisms of suppuration. The examination of a large num- 

 ber of milk samples in a city bacteriological laboratory by a 

 fairly rapid, accurate method would perhaps obviate numerous 

 visits to the dairies. In case of -positive results, the dairies 

 might be visited and inspected for udder disease or the milk 

 of the individual animals in turn examined by the same test as 

 a more delicate method than physical examination for selecting 

 those cows yielding pus cells. 



Stokes' test. Stokes (29) centrifugalized 10 cc. of milk, 

 smeared the sediment on a cover glass and stained. When 



