268 MILK 



The number of bacteria in milk while in the udder is usually 

 small, and probably earlier examinations have failed to detect 

 their presence, because but small amounts of milk were actually 

 examined. When large amounts are used, as in experiments of 

 Bolley and Hall, absence of bacteria is a rare occurrence; in fact, 

 Moore was never able to obtain even a small amount of milk 

 that was germ free. Boekhout and de Vries took 320 samples of 

 milk, each one 15 c.c., without finding a single one sterile. 



It is true that sometimes with rigid aseptic precautions milk 

 that seems to contain no bacteria can be obtained from the udder. 

 Bergey obtained such milk in about one-third of the samples 

 examined. A similar result was obtained by the writer. In 

 examining 45 samples of strippings, 15 plates remained sterile. 

 However, since but 0.2 c.c. of milk was plated from each sample, 

 it is quite likely that the presence of bacteria would have been 

 detected if larger quantities had been used. 



Approaching the problem from a different direction, Simon 

 found no bacteria in the glands of 9 udders from freshly slaugh- 

 tered cows, while in the udders of 3 other cows streptococci were 

 present. These latter ones, however, came from diseased cows. 

 Ward, on the other hand, found bacteria in all parts of udders from 

 freshly slaughtered cows. Barthel obtained results similar to those 

 of Ward, but after investigation of the kinds of bacteria present 

 he doubted the accuracy of his results, because the same types 

 of bacteria occurred in the stable air and in the milk from the 

 slaughtered animal. It does not seem, however, that these find- 

 ings militate against the interpretation that bacteria were actually 

 present in the udder, since the view held by modern investigators 

 holds that micro-organisms gain access to the udder from without. 



The question of the origin of bacteria in the udder has occu- 

 pied the attention of investigators to a considerable degree. It 

 is now generally accepted that bacteria do not enter the milk from 

 the mammary gland unless it is in an abnormal condition. Base- 

 nau's observation that Bacillus morbificans when injected into a 

 cow can be recovered from the milk does not prove that bacteria 

 pass through healthy mammary glands. According to Basch 

 and Weleminsky, only those bacteria can pass through the mam- 

 mary glands that cause hemorrhagic lesions or other abnormal 

 conditions that alter the normal state of the udder. Mixing 

 cultures with food, as Ward did, using Bacillus prodigiosus, pro- 

 duced negative results. Whether ultramicroscopic organisms, as 

 the organism of foot-and-mouth disease, can be communicated 

 to milk through the secreting glands is a problem that has not 

 yet been solved. 



When all the evidence pro and con of the existence of bacteria 



