Fermentations of Milk. 95 



can be produced in a second sample by transferring a 

 little of the slimy milk to it. 



The fermentation produced by the aerobic bacteria is 

 most often met in bottled milk and cream during the 

 warmer times of the year. On account of their relation 

 to oxygen, the growth is confined to the surface of the 

 milk and only the upper layer becomes slimy ; thus when 

 the cream is removed, the abnormal condition is noted. 

 The sliminess is due to the mass of bacterial growth 

 rather than to the production of any specific substance 

 in the milk. This trouble may be of considerable eco- 

 nomic importance to the dealer, as such abnormal milk is 

 objectionable for ordinary use, but as far as is known, 

 it is incapable of affecting the health of the consumer. 



In numerous outbreaks of this trouble the source of 

 contamination has been traced to infection from well 

 water or a stream, as the organisms causing the trouble 

 are found naturally in water. Keeping the milk in a 

 tank in the pump house sometimes permits of troubles of 

 this sort, the water used for cooling giving opportunity 

 for contamination. Cattle wading in a stream sometimes 

 pollute their udders and so indirectly infect the milk. 

 Such outbreaks rarely persist for any considerable length 

 of time as the common acid organisms soon regain the 

 ascendency. 



Creameries and cheese factories are sometimes troubled 

 with sliminess in starters. This seems to be due to some 

 change which the ordinary lactic acid bacteria undergo 

 on long propagation rather than to contamination of the 

 starter. There are, however, types of acid-producing 

 bacteria that are able to form specific substances in milk 

 that are slimy in character. Two of these forms of slimy 

 milk are of economic importance. The slimy whey (lange 



