136 MICRO-ORGANISMS AND FERMENTATION. 



" kephir-grains," to milk. These are white or yellowish and 

 irregularly-shaped grains, not larger than a walnut and of a 

 tough gelatinous consistency, and when dried become cartila- 

 ginous and brittle. The essential part of these grains consists 

 of rod-like bacteria, connected in threads, and enveloped in 

 gelatinous membranes. Kern calls this bacterium Dispora 

 Caucasica. According to Beijerinck this species, which he calls 

 Lactobacillus caucasicus, produces in lactose, saccharose, glucose, 

 and maltose a direct lactic acid fermentation. It produces 

 solid, nodular colonies on whey gelatine resembling the kephir- 

 grains. Besides bacteria, various yeast fungi and, frequently, 

 moulds occur in the kephir-grains. 



In the preparation of kephir a little milk is first poured 

 on the grains and allowed to stand for twenty-four hours at 

 about 17 C. ; the milk is then poured off, and the grains 

 preserved for future use. This milk is mixed with fresh milk, 

 and poured into closed bottles, or leather sacks ; the fer- 

 mentation is completed in two or three days if the liquid is 

 frequently shaken. It now contains about 2 per cent, of 

 alcohol. This result is probably brought about by the simul- 

 taneous action of Dispora and yeast cells in combination with 

 lactic acid bacteria present in milk. These ferments convert 

 a portion of the lactose into lactic acid ; the alcohol and a part 

 of the carbon dioxide result from the action of yeast. As the 

 fermented milk, according to some authorities, contains less 

 coagulated casein than ordinary sour milk, it may be assumed 

 that the Dispora is also able to partly liquefy (peptonise) 

 the coagulated casein, perhaps with the help of the gelatinous 

 mass secreted by the bacterium, found in the kephir-grains, 

 but not present in the fermenting milk. According to recent 

 investigations of Hammarsten, however, the amount of 

 casein does not appear to decrease, but a part of it undergoes 

 certain alterations, partly physical, in consequence of which 

 it becomes more finely flocculent. The want of agreement 

 in these results may possibly originate in the different biological 

 composition of the selected kephir-grains. 



Freudenreich regularly found Dispora Caucasica (Bac. 

 Caucasicus) in a number of kephir samples, which readily 

 developed on milk-agar plates and in lactose broth at 35 C. ; 



