ACETIC FEEMENTATION. 73 



germs cannot become fertile because of the absence of 

 their indispensable food. Wine in bottles well filled 

 and laid flat do not acetify ; this is because the myco- 

 derm cannot multiply for lack of oxygen. Without 

 doubt the air constantly penetrates through the pores 

 of the cork, but always in such feeble quantities that 

 the colouring matters of the wine, and other more or 

 less oxydisable constituents, take possession of it with- 

 out leaving the smallest quantity for the germs of the 

 mycoderm which are generally suspended in the 

 wine. When the bottle is upright the conditions are 

 quite altered. The desiccation of the cork renders it 

 much more permeable to the air, and the germs of 

 the mycoderm on the surface of the liquid, if any 

 exist there, are enveloped by air. 



Thus, to recapitulate in a few words the principles 

 which have just been established ; it is easy to see that 

 the formation of vinegar is always preceded by the de- 

 velopment, on the surface of the wine, of a little plant 

 formed of strangulated particles, of an extreme tenuity, 

 and the accumulation of which sometimes takes the 

 form of a hardly visible veil, sometimes of a wrinkled 

 film of very slight thickness, and greasy to the touch, 

 because of the various fatty matters which the plant 

 contains. 



This cryptogam has the singular property of con- 

 densing considerable quantities of oxygen and of pro- 

 voking the fixation of this gas upon the alcohol, which 



