EQUATION OF ACETIC FERMENTATION. 397 



We are indebted to G. BERTRAND (I.) for a beautiful experiment 

 with a fission fungus, not accurately identified, but presumably 

 very closely allied to Bacterium xylinum. Mountain-ash berries, 

 i.e. the fruit of Sorbus aucuparia, S. intermedia, and S. latifolia, 

 contain, in addition to glucose, an alcohol isomeric with mannite, 

 viz., Sorbitol (C 6 H 14 6 ). If now the juice of these berries be 

 subjected to alcoholic fermentation (which sets in rapidly and 

 spontaneously), the glucose is decomposed, but not the sorbitol, 

 this latter only being attacked when the above-mentioned fission 

 fungus obtains access into the fermented liquid, which it does 

 through the mediation of a small red fly (Drosophila funelris, 

 Fabricius, D. cellaris, Macquart), known to all fermentation tech- 

 nicists as the "vinegar-fly." This insect haunts places where alco- 

 holic juices (especially fermented fruit-juices) are being stored 

 and converted into vinegar, and there loads itself with acetic acid 

 bacteria, which it then transfers to other localities. The bacterium 

 introduced by these flies into the fermented juice of the mountain- 

 ash berry oxidises the hexavalent alcohol sorbitol to the ketose 

 sorbin (also known as sorbinose or sorbose), according to the 

 equation 



C 6 H 14 6 + O = C 6 H 12 6 + H 2 0. 



This affords a convenient method for the production of sorbose. 



With regard to the fermentative capacity of B. aceti Hansen, 

 and B. Pasteurianum, the author, in 1895, published comparative 

 investigations, showing that a sowing of the first-named species on 

 pale lager-beer is able to develop and exert a powerful acidifying 

 effect at 4-4.5 C. ; whereas B. Pasteurianum is unable to do this, 

 or to reproduce itself at all, even at 4.5-5 C. 



213. Pure Culture Ferments in the Manufacture 

 of Vinegar. 



Searching investigations into the chemical activity of the 

 different species of acetic acid bacteria would be not only opportune 

 in the interests of science, but also highly important to the prac- 

 tice of the vinegar industry. In this business the employment of 

 selected pure culture ferments is not yet regarded as a fundamental 

 rule, everything being still left to the mercy of chance. 



As every reader will be aware, there are two different methods 

 of making vinegar. In one of them wine forms the raw material, 

 this method being known as the Orleans process, from having long 

 been extensively carried on in that locality. There (as elsewhere) 

 the work is still performed in the same manner as it was centuries 

 ago, as follows : A number of oaken casks, each of a capacity of 

 some 55 gallons, are arranged in rows in a chamber maintained at 

 a constant temperature of 1 8 to 22 C. In the upper part of the 

 front end (head) of each cask a circular aperture (a few c.m. in 



