186 MODERN DAIRY PRACTICE. 



not retain a too thick layer of slime in the bowl, and if 

 much filth is accumulated on it, part of it will again be 

 washed off and will mix in the cream and the skim-milk. 

 To prevent this new infection we must avoid running the 

 separators many hours without interruption, and special 

 attention must be given to their cleaning. When con- 

 ducted in the right way the separation will, however, im- 

 prove the milk, decrease its bacterial content, clean it and 

 make it keep better. 



The results of my investigations thus differ from those 

 obtained by Professor Fjord in Denmark in his investiga- 

 tions of separator skim-milk, where he found that centri- 

 fuging the milk neither injures nor improves its keeping 

 quality. He doubtless worked with highly-infected milk 

 containing large quantities of bacteria even after the 

 separation, and these soon made their influence felt at the 

 high temperature applied. 



The nature of the different bacteria may also be of some 

 importance in regard to this question. In making similar 

 boiling experiments of separator skim-milk as conducted by 

 Fjord in the investigation mentioned, I have as a rule been 

 able to prove a very high keeping-quality in the separator 

 milk. Exceptions always occurred in cases where the milk 

 was very rich in bacteria before the separation. 



[Scheuerlen has also shown that even strong separation 

 only partially purifies a highly infected milk from bacteria, 

 and different kinds of bacteria behave differently under the 

 influence of centrifugal force. He calls special attention to 

 the fact that tubercle bacilli and some lactic-acid bacteria 

 are easily separated into the slime in separation, while, e.g., 

 the typhus bacillum is usually found in the cream.*] 

 * Author's addition to American translation. 



