20 DEPARTMENT BULLETIN 319, U. S. DEPT. OF AGRICULTURE 
with rennet a softer, more friable curd, but it is not certain that this 
property would increase the value of kumiss. 
Kumiss is 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, a preparation quite distinct from that of the Caucasus and 
the Russian steppes is found. 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 quick-curdled milks, decidedly acid, 
and with very little or no alcohol. The method of preparation is also 
very different. 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 original volume. In the latter case it is not used as a drink, but is 
eaten, frequentty 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, it lias no seeds through which the fermen- 
tation can be transmitted, but the essential organism is sometimes 
preserved by drying the fermented milk and reducing the dry mate- 
rial to a powder. This constitutes the podkwassa, or maya. The 
organism giving these milks their distinctive character is evidently 
identical in them all, or, more properly speaking, may be any one of 
the several varieties of a distinct and closely related group. On ac- 
count of its peculiarities, some of which are exceptional and striking, 
and the importance attached to it by discussions both in the scientific 
and the popular press, a brief resume of its characteristics is given : 
This bacterium was probabty first observed by Kern (47), who 
incorrectly designated it as Dispora caucasicum. His description, 
however, is so limited that it is impossible to attach the name he pro- 
poses to any particular organism. Later Beyerinck (7), described 
under the name Bacterium caucasicum, and Freudenreich (28), as 
Bacillus caucasicus, organisms isolated from kefir which agree in their 
essential features with those obtained from yogurt, Kist and 
Khoury (78) isolated from Egyptian leben two bacilli to which they 
gave the names Strepto-bacillus lebensis and Bacillus lebenis. Grig- 
oroff (32) and Cohendy (15) isolated similar organisms from Bul- 
garian fermented milk. These various bacteria are undoubtedly 
nearly or quite identical, and all are included under the name Lacto- 
bacillus bulgaricus, now generally adopted. Work by Hastings (35) 
and by Heinemann and Hefferan (39) indicates that this bacterium 
is not peculiar to the eastern fermented milks, but is widely distrib- 
uted, having been isolated from milk, soil, saliva, feces, and various 
soured foods. White and Avery (91) believe that this bacterium is 
the representative of a group of closely related bacteria which they 
divide into two types on the basis of their activity in milk and the 
nature of the lactic acid formed. The action of this organism on 
milk distinguishes it from all other known bacteria. At the optimum 
temperature milk is curdled in a few hours with a rather soft curd, 
