ACETIC FERMENTATION. 53 



from the families Mucedvtes, Ahuorina, Torulce, &c. The fermen- 

 tations these plants produce, are commonly called " after fermen- 

 tations." M. Pasteur calls them "diseased," because their propagation 

 and development is always attended with the loss of Sugar, or Alcohol, 

 and also with the production of some unpalatable result. To apply 

 this rule to our present subject, the Cider or Perry may thus become 

 acid, viscous (ropy), or be altogether spoilt, according as the germ 

 of the several funguses, which produces these results, have been 

 able to develop themselves within it. 



Acetic Fermentation. — The fungus which causes this dread- 

 ed fermentation is the Mycoderma Aceti. Its germs are so minute 

 as to be only perceptible with a powerful microscope when they are 

 diffused in the liquor ; but when aided by exposure to air under a 

 high temperature, they are quickly developed into chains and chap- 

 lets, which ma:sed together, soon appear as a film of grey mould 

 floating on the surface, and this is commonly called " flowers of 

 vinegar." When this film has grown thicker and become sub- 

 merged, it takes on a gelatinous form of surprising toughness and 

 lubricity, and it is then caUed the " Mother of Vinegar," or the 

 " Vinegar Plant." The Mycoderma Aceti requires a warm temper- 

 ature, and a much more abundant supply of air, than do those 

 Saccharomyces, which cause Alcoholic fermentation, and the more 

 freely air is supplied the more rapidly the plant grows, and the more 

 quickly is the vinegar produced. The Mycoderma Aceti has the 

 power of decomposing Sugar, or Alcohol, either singly or in com- 

 bination, producing Acetic Acid and water, without the evolution of 

 Carbonic Acid gas. When the access of air is prevented, as should 

 always be the first care of the Wine or Cider maker, its action is 

 extremely slow. It is sure, nevertheless ; for the germs that find 

 their way with the liquor into closed vessels and well-corked bottles 

 will prevail in the long run ; thus an excellent bottle of Wine or 

 Cider will end in becoming a bottle of Vinegar, though it may take 

 half a century to effect the change. 



Viscous Fermentation, or Ropiness. — This "disease" is also 

 caused by the rapid growth of the minute spherical germs of a 

 fungus, not as yet specifically named. It quickly develops itself 



