BACTERIA. 81 



(prepared cold), and later more accurately described' by H. 

 BUCHNER (Fig. 22), which occurs with coccus and bacillus 

 forms. In a nutritive solution containing glycerine it 

 ferments this latter substance, forming chiefly ethyl alcohol. 

 The Bacillus ethaceticus, discovered by P. FRANKLAND, fer- 

 ments glycerine, mannite, or arabinose, forming ethyl alcohol 

 in conjunction with acetic acid. Finally, the Bacillus pneu- 

 monia of FRIEDLAENDER may be mentioned, which is not only 

 a pathogenic organism, but also, in nutritive sugar solutions, 

 forms ethyl alcohol, acetic acid, and other products. 



As stated above, one of the fermentation products of the 

 three species of butyric acid bacteria, described by GRUBER, is 

 butyl alcohol. BEIJERINCK includes all bacteria giving a butyl 

 alcohol fermentation under the designation of Granulobacter , 

 because in the absence of oxygen they form granulose, and 

 are then coloured blue by iodine. The species described by 

 this author are probably identical with the butyric acid 

 bacteria of PRAZMOWSKI, FITZ, and GRUBER. 



5. KEPHIR-ORGANISMS AND GINGER-BEER PLANT. 



The so-called " Kephir" on which the investigations of 

 KERN have thrown some light, is an effervescent, alcoholic 

 and sour milk, which is prepared by the inhabitants of the 

 Caucasus from cows', goats', or sheep's milk. It is prepared 

 by adding a peculiar ferment, " kephir-grains," to milk. 

 These are white or yellowish, irregularly-shaped, uneven 

 grains, about the size of a walnut and of a tough gelatinous 

 consistency, and when dried become cartilaginous and brittle. 

 The essential part of these grains consists of rod-like bacteria, 

 which are connected in threads and have developed gelatinous 

 membranes. KERN calls this bacterium Dispora Caucasica. 

 According to BEIJERINCK this species produces in milk-sugar, 

 cane-sugar, glucose, and maltose a direct lactic acid fer- 

 mentation. Besides the bacteria, there occur in the kephir- 

 grains various yeast fungi and, frequently, moulds. 



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 



F 



