20 BULLETIN 319, U. S. DEPARTMENT OP 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- 

 casians, 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-bacillus lebensis and Bacillus 

 lebenis. Grigoroff (29) and Cohendy (13) isolated similar organ- 

 isms from Bulgarian fermented milk. These various bacteria are 



