Mother of Vinegar 467 



the optimum, the long chains break up into the short 

 rods. Apart from temperature, the age of the inocu- 

 lating material and the composition of the liquid are 

 of considerable influence in the formation of the extremely 

 long or of the thickened cells. The proportion of acid 

 in the liquid is of importance here, for with increasing 

 acidity the degeneration forms become prominent even 

 at optimum temperatures, and a point is finally reached 

 when most of the cells die off on account of the unfavor- 

 able conditions. 



Acetic-acid bacteria. — These bacteria are distinguished 

 for their abihty to oxidize not only alcohol, but a whole 

 series of other compounds. The products formed de- 

 pend entirely on the nature of the original substance. 

 For instance, oxaHc acid is made by them out of grape- 

 sugar, cane-sugar, milk-sugar, and the like, the differ- 

 ent species showing marked variations as to preference 

 for certain compounds. Other compounds made by 

 acetic -acid ferments include glycerine, mannite, butyric 

 acid, gluconic acid, levulose, and various other substances. 

 Moreover, the acetic acid itself made by the ferments 

 out of grain alcohol may be burned up further to car- 

 bon dioxid and water. 



This accounts for the fact that in sour wine, cider, 

 and similar compounds, the acid accumulates up to a 

 certain point and then begins to decrease in amount 

 until, in some extreme cases, all of it has been used. 

 Under such conditions, the ordinary decay bacteria are 

 no longer kept out by the acid and the liquid undergoes 

 putrefaction. The disappearance of the acetic acid in 

 vinegar is favored by its dilution, for, having changed 



