Cream and Factory By-Products. 119 



The bacterial content of each of these will vary materially 

 in different cases. 



The slime which is composed of particles having a 

 greater specific gravity than the milk serum is thrown out 

 on the edge of the revolving fluid by centrifugal force. 

 This material, if examined microscopically, will be found 

 to contain large quantities of foreign matter as well as 

 innumerable bacteria. The fact that it rapidly undergoes 

 decomposition is evidence of its high germ content. 



The cream will almost always contain a larger number 

 of bacteria than the skim-milk. Popp and Becker found 

 in a sample of whole milk containing 73,000 germs per cc. , 

 the following germ contents after it had been separated: 

 Cream, 58, 275 germs; skim-milk, 21,700 germs, and the 

 separator slime 43, 900 per cc. This centripetal niovement 

 of a large number of germs with the cream indicates that 

 they adhere to the tiny fat globules, for this peculiarity 

 in distribution can hardly be explained on the ground of 

 their specific gravity, as they remain in the skim-milk in 

 considerable numbers in spite of the great centrifugal 

 pressure . 



115. Tubercle bacillus and separator slime. Ac- 

 cording to Scheurlen 1 and Bang 2 , tubercle bacilli, if 

 present in a milk are largely thrown out with the slime 

 in the separating process. Moore 3 found in milk arti- 

 ficially infected with tubercle bacilli that the separating 

 process diminished them to such an extent that they 

 could not be determined microscopically, but when this 

 separated milk was inoculated into guinea-pigs, infection 

 occurred. This indicates that while the removal was con- 

 siderable, yet it was not complete enough to justify the 



1 Scheurlen, Arb. a. d. k. Ges. Amte, 7: 269, 1891. 



2 Bang, Land. Woch. f. Sch. Hoi., 1894, p. 47. 



3 Moore, Year-book of U. S. Dept. of Agri. 1895, p. 432. 



