282 AGRICULTURAL BACTERIOLOGY. 



about forty gallons (two-thirds full). Then about half of the 

 material is withdrawn as vinegar, and from this time on some 

 two gallons of vinegar may be withdrawn at a time, its place 

 being made good by the addition of wine. The cask when 

 once started may continue in operation for six to eight years 

 without interruption, but eventually it becomes so filled with 

 tartar and mother of vinegar that it must be cleansed. 



Shortly after the process of vinegar-making has started a 

 skin of the Mycoderma grows on the surface. This soon 

 covers the whole, and its action produces the vinegar. At the 

 outset the proper vinegar organisms are apt to be few in num- 

 ber and other bacteria get a chance to develop. Consequently, 

 in recent years, the method has been widely adopted of culti- 

 vating the mother in special cultures, on the surface of wine 

 that is soured in open dishes or vats. A small amount of this 

 culture is then placed in the wine to start the growth of the 

 " mother," and from this inoculation it spreads rapidly. 



After the scum is produced the vinegar formation begins. 

 Exactly how the organisms produce the result we do not 

 know, but in some way they cause the alcohol to unite with 

 oxygen from the air and thus become converted into acetic 

 acid. The oxidation is doubtless in some way a benefit to the 

 plants, for they grow luxuriantly during the process. The 

 oxidation does not always stop at the formation of acetic acid, 

 but is sometimes carried further so as to split up the alcohol 

 into simpler molecules. This results in a loss, and is one of 

 the difficulties to be met with in the vinegar manufacture. 

 The loss is commonly not great, for the accumulation of acetic 

 acid will soon stop the growth of the organisms, since they 

 are unable to grow after the acetic acid has become abundant. 

 Different species of the organisms can endure a different 

 amount, but when the acetic acid has reached 14 per cent, the 

 bacteria are never able to produce any more. A serious loss 

 to the manufacturer arises from the different powers of different 



