247 



keep well. This germ is easily killed by heat and disinfect- 

 ants, but it will survive a long period of drying. 



Yellow Milk may appear as the result of the action of sev- 

 eral species of germs. Some of these precipitate and then 

 dissolve the casein. Some produce a bright lemon color in 

 milk, while others give the milk an orange tint. Violet and 

 green tints may be produced by certain pigment-producing 

 germs. These germs are rarely found in milk. When they 

 occar, myre attention to cleanliness will eliminate them from 

 the dairy. 



The Yeasts usually produce in milk an alcoholic fermenta- 

 tion ; they change the milk sugar into alcohol, water and 

 carbonic acid gas. Skimmed milk may be inoculated with 

 yeast and a very nutritive drink, called kephir or koumiss, 

 will be pioduced. Kephir is usually made from cows' milk, 

 while koumiss is made from mares' milk. Yeast fungi are 

 the predominating organisms in these alcoholic fermentations 

 of milk ; but there may be some bacteria and molds in the 

 mixture. Koumiss is said to be more easily digested 

 than milk and is sometimes given to invalids instead of milk. 



Casein Ferments are all spore-forming bacteria, and con- 

 sequently are very difficult to destroy. The tyrotherix group 

 of bacteria, first studied by Duclaux, and the potato bacillus 

 {bacillus mesentericus vulgatus) and the bacillus sxibtilis are 

 some of the germs that produce casein fermentation. Some 

 germs may break up or decompose the casein and produce 

 unpleasant smelling gases, carbonic acid gas, ammonia and 

 water; such germs usually decompose the casein without 

 precipitating it. Other germs may precipitate and then 

 dissolve the casein. Still other casein ferments simply coag- 

 ulate the casein ; some of these coagulate the casein very like 

 the rennet ferment. In fact Conn has prepared a germ in the 

 form of a dry powder, which acts like rennet on milk casein. 

 Casein ferments may act after the lactic fermentation is 

 completed; and, "in all probability, they are intimately con- 

 cerned in the curing of cheese in which the casein is broken 

 down into soluble compounds." (Russell.) 



