OP ARTS AND SCIENCES. 109 



Another way in which this American milk-ferment resembles 

 kephir is, that it causes alcoholic fermentation of dextrose. De Bary 

 is authority for the statement, that the "• kephir yeast, like its con- 

 stituent the Saccharomycete, working by itself, gives rise to alcobolic 

 fermentation in a nutrient solution of grape-sugar, though of a less 

 active kind than that caused by beer-yeast." * The specimen which 

 I had gave a good alcoholic fermentation with dextrose solutions, but 

 caused no fermentation with saccharose. It seems, therefore, to have 

 the power of fermenting only two of our natural sugars, — dextrose 

 and milk-sugar. 



When we consider the remarkable similarity of these American 

 grains with the kephir granules in color, shape, and general appear- 

 ance; the great similarity between the j^east cells and bacteria of 

 each in appearance, habits, mode of growth, form, and size; the fact 

 that both of these yeasts cause alcoholic fermentation of milk ; the 

 fact that the drink formed by the American kephir closely resembles 

 the description of kephir ; the minor resemblance between the two, 

 that of fermenting dextrose solutions, and that of its great capacity 

 for resisting external influences, — we are justified in concluding the 

 American milk-ferment to be a very near relative of the European 

 kephir, if it be not indeed identical with it. 



One point remains, viz. How can this yeast cause alcoholic fermen- 

 tation of milk-sugar ? This question, which did not present itself to 

 Kern, De Bary has tried to explain in his ' Lectures on Bacteria.' 

 Speaking of kephir, he says, " The changes in the milk which produce 

 the drink here described are brought about by the combined activity 

 of at least three ferment-organisms." There is the yeast cell, the 

 Bacillus of the kephir-grain, and the Bacterium of lactic fermentation. 

 He goes on to say that " the acidification is caused by the conversion 

 of a portion of the milk-sugar into lactic acid by the bacterium of that 

 acid. The alcoholic fermentation, that is, the formation of alcohol 

 and of a large part at least of the carbonic acid, is indebted for its 

 material to another portion of the milk-sugar, and for its existence to 

 the fermenting power of the Sprouting Fungus (yeast). , . . But al- 

 coholic fermentation is produced in milk-sugar as such neither by Sac- 

 charomycetes, with which we are acquainted, nor, as experiment has 

 shown, by those of which we are speaking. To make this fermenta- 

 tion possible the sugar must first be inverted, split into fermentable 

 kinds of sugar." De Bary continues: "According to Nageli, the for- 



* Lectures on Bacteria, De Bary, translated by Garnsey and Balfour, p. 96. 



