20 BULLETIN 319, U. S. DEPARTMENT OF AGRICULTURE. 
nitrogenous part of the milk except the possible advantage of a 
finely divided curd. Mare's milk differs from cow's milk in giving 
with rennet a softer, more friable curd, but it is not certain that this 
property would increase the value of kumiss. 
Kumiss is often made and offered for sale in this country, but as 
this is usually made from cow's milk, it is, more correctly, kefir. 
YOGURT. 
In passing to a consideration of the fermented milks used by the 
people of the countries bordering on the eastern end of the Mediter- 
ranean we find a preparation very distinct from that of the Caucasus 
and the Russian steppes. Kefir and kumiss are limpid, mildly acid, 
and distinctly alcoholic; but the yogurt, yahourth, or jugurt of the 
Turks, the kisselo mleko of the Balkan people, the mazun of Armenia, 
the gioddu of Sardinia, the dadhi of India, and the leben or leben raib 
of Egypt, are all thick-curdled milks, decidedly acid, and with very 
little or no alcohol. The method of preparation is also quite differ- 
ent. Goat's, buffalo's, or cow's milk may be used. This is usually 
boiled and sometimes is reduced by evaporation to one-half its origi- 
nal volume. In the latter case it is not used as a drink, but is eaten, 
frequently with the addition of bread, dates, or other food. 
A portion of the previously fermented milk is used to ferment the 
fresh milk. Unlike kefir, there are no "seeds" through which the 
fermentation can be transmitted, but the essential organism is some- 
times preserved by drying the fermented milk and reducing the dry 
material to a powder. This constitutes the " podkwassa," or " maya." 
The organism giving these milks their distinctive character is evi- 
dently identical in them all, or, more properly speaking, may be 
any one of the several varieties of a distinct and closely related group. 
On account of its peculiarities, some of which are exceptional and 
striking, and the importance recently attached to it by the discus- 
sions both in the scientific and the popular press, a brief resume of 
its characteristics is given : 
This bacterium was probably first observed by Kern (45), who 
incorrectly designated it Dispora caucasicum. His description, how- 
ever, is so limited that it is impossible to attach the name he pro- 
poses to any particular organism. Later Beyerinck (6), under the 
name Bacterium caucasicum, and Freudenreich (25), as Bacillus cau- 
casicus, described organisms isolated from kefir which agree in their 
essential features with those obtained from yogurt. More recently 
Rist and Khoury (72) isolated from Egyptian leben two bacilli to 
which they gave the names Strepto-baciUus lebensis and Bacillus 
lebenis. Grigoroff (29) and Cohendy (13) isolated similar organ- 
isms from Bulgarian fermented milk. These various bacteria are 
