2 THE CONTAMINATION OF MILK. 



(5, 25, 27, 28, 47). The conclusions drawn from this line of 

 work have been in substantial agreement upon the point that 

 milk is contaminated before it reaches the teats. The subject 

 is further treated in references 4, 9, 26, 31, 32, 68. 



The number of bacteria found in the udder is less than 

 would be expected elsewhere under similar conditions of food, 

 moisture and temperature away from vital influences. The 

 germicidal influence of fresh milk has been cited as an explan- 

 ation of the fact (25, 28). The last of the milk drawn at 

 any one milking contains less bacteria than that first drawn, 

 but is seldom found to be sterile, if any but minute quantities 

 are taken for examination. In fact, the " strippings " have 

 been found to contain more bacteria per cc. than that drawn 

 immediately before stripping. If a cow is not stripped, — that 

 is, if a little milk is left in the udder, — the next milking will 

 show a number of bacteria larger than usual. This fact has 

 been explained by assuming that thorough milking removes 

 the bacteria from the milk ducts more completely than the 

 ordinary milking (60). It is evident that the few bacteria 

 remaining in the ducts after milking constitute the source of 

 the relatively larger numbers in the milk obtained during the 

 fore and middle portions of the succeeding milking. It is not 

 believed that the udder is subject to indiscriminate invasion by 

 a variety of forms, but rather that the conditions found there 

 are such as limit the bacterial flora. A number of attempts to 

 colonize the udder with a variety of organisms have not met 

 with success. Bacillus prodigiosus, an organism easily recog- 

 nized in cultures by the red color, has been used several times 

 with the result that inflammatory conditions have been set up. 

 The observed persistence of this organism for twenty-two days, 

 while the udder was inflamed, does not prove much, in view 

 of the disease, and it was obtained in constantly decreasing 

 numbers, which led to the conclusion that multiplication had 

 not occurred (53). In one instance the teat of a goat was 

 injected with B. prodigiosus and after slaughter, three days 

 later, cultures showed that the organisms had invaded the 

 udder (25). The fact that this particular organism is not 

 an udder organism, and was used on account of its chromo- 



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