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 
