398 ACETIC FERMENTATION. 



width) is provided, through which the cask can be filled or emptied, 

 and which is generally kept closed, whilst near it is a very small 

 hole (vent) always left open for the admission of air. In normal 

 work each cask is about half full. Before setting a new cask in 

 work, it is scalded out several times with steam or hot water, in 

 order to extract the sap from the M r ood, and is then "soured" by 

 impregnating it with good, boiling-hot vinegar. About i h.l. (22 

 galls.) of good clear vinegar and 2 1. (0.44 gall.) of wine are then 

 placed in the cask, another 3 1. of wine being added at the end of 

 eight days, 4 to 5 1. more after the lapse of another week, and so 

 on until the cask contains about 180-200 1. (40-44 galls.). Then, 

 for the first time, vinegar is drawn from the cask, and in such 

 quantity that about 22 galls, are left behind in the vessel. From 

 that time the cask ("mother") is in continuous use, 10 litres (2.2 

 galls.) of vinegar being withdrawn every week and replaced by an 

 equal quantity of wine. The " mother " casks may remain in work 

 during six or eight years without interruption, but at the end 

 of this period they will contain such a considerable accumulation 

 of deposited yeast, tartar and mother of vinegar, as to necessitate 

 their being emptied and cleansed. A skin, known as vinegar- 

 flowers or mother of vinegar, and composed of acetic acid bacteria, 

 develops on the surface of the liquid, and the manner and luxuri- 

 ance of its growth enables the operator to judge the progress of 

 the fermentation. However, at the outset the growth proceeds 

 very slowly, since the wine employed mostly contains but very 

 few of these bacteria. Consequently an opportunity is afforded for 

 the development of rapid - growing injurious organisms, chiefly 

 certain budding fungi, which consume the acetic acid. The 

 aerobic " vinegar eels " also make their appearance. To obviate 

 this source of loss, PASTEUR (XV.), in 1862. proposed that, instead 

 of waiting until the acetic acid bacteria in the wine had increased 

 sufficiently to form a protective skin of " vinegar-flowers," the 

 necessary ferment should be cultivated in small vessels, the skin 

 thus obtained being then carefully transferred in pieces of suffi- 

 cient size, by the aid of a wooden spatula, on to the surface of the 

 wine to be soured, which was placed in shallow open vats. This 

 process was adopted by Breton-Lorion of Orleans, in particular, 

 and would be suitable for general application if the presence of 

 not more than one species of acetic ferment could be thereby 

 ensured. This, however, is not the case, and it is purely a matter 

 of chance whether the skin prepared by cultivation beforehand is 

 composed of beneficial or injurious organisms. According to cir- 

 cumstance?, there may be present several very different species 

 with divergent properties, faculties, conditions of vitality and 

 metabolic products. By reason of this uncertainty alone, the 

 Pasteur method is liable to produce very irregular results, and 

 may, on occasion, actually give rise to losses ; and, as a matter of 

 fact, it is just on this account that the method has been aban- 



