158 BACTERIA IN MILK. 



now an imitation product is widely made and used, prepared from 

 cow's milk. A small quantity of sugar is added to milk and some 

 common baker's yeast. An alcoholic fermentation soon begins, 

 and the fermented product is kummys. Various modifications of 

 this general process are adopted by different makers, for kummys 

 has become a commercial article. 



In addition to these there are several other types of beverages 

 made from milk in common use among different nations, in the 

 production of which alcohol is formed. One, known as kefir, 

 has long been used in the Caucasus mountains. The fermentation 



FIG. 39. A large-sized kefir grain and the three species of bacteria of 

 which it is composed (Freudenreich). 



is brought about by adding to the milk what are known as kefir 

 grains (Fig. 39). These are hard nodules of various sizes which 

 have the power of starting an alcoholic fermentation in ordinary 

 cow's milk. The origin of these kefir grains is unknown. To- 

 day they are handed from person to person, taken from the fer- 

 mented milk and dried to be used again. During the fermentation 

 in the milk they increase in size and new grains may be obtained 

 from fragments of the old ones. In Egypt the people use a fermented 

 milk called leben. Another, called mazoon, is common in Armenia. 

 The Turks have one they call yoghourt, and in Sardinia still another 

 is found with the name of goiddu. In all these cases the beverage 

 is prepared by the use of ferments that the people keep on hand, 

 whose original sources are unknown. These ferments, so far as 



