94 THE TYPES OF MILK BACTERIA. 



ducts, and in the course of a couple of days it contains a 

 quantity of alcohol and carbonic acid and is ready to drink. 

 During this time the Kefir grains increase in size. After 

 the fermentation they are removed and either dried for pre- 

 servation or placed again immediately in other flasks cf milk 

 for a repetition of the process. The grains are very care- 

 fully preserved as great treasures. The growth of the grains 

 makes it possible to distribute them, and thus the material 

 is carried from place to place. The production of Kefir is, 

 therefore, the result of the action of the Kefir grains. 



Although these grains have been much studied there has 

 been no agreement as to their real nature. That they con- 

 sist of a variety of microorganisms is easily proved, and that 

 they contain yeasts, bacilli and cocci has also been uni- 

 formly recognized. But there is lack of agreement as to 

 the relation of these microorganisms, and which of them are 

 important and which purely incidental. The most recent, 

 and probably the most reliable work, indicates that there are 

 in Kefir grains four different microorganisms, a species of 

 yeast, two species of streptococci and a peculiar bacillus 

 called B. Caucasus (95). The last, which was originally 

 described as especially characteristic of the Kefir grains, 

 probably has no special relation to the production of the 

 alcoholic fermentation. At all events it has been found pos- 

 sible to produce the Kefir fermentation by the use of the 

 yeasts and the streptococci without the aid of the B. Cau- 

 casus. The role of this bacterium in producing this fer- 

 mentation is, therefore, at present unknown. Kefir can be 

 produced by adding the Kefir yeast to milk with a little citric 

 acid. 



Leben. An Egyptian Fermented Milk. There has re- 

 cently been described an alcoholic fermented milk, used 

 to some extent by the peasants in Egypt, called " leben " 

 (96) . It has been known for centuries and is prepared from 

 milk of the buffalo, cow or goat. The fermentation is propa- 



