96 MICEOBES, FERMENTS, AND MOULDS. 



chains or curved rods. They multiply by the trans- 

 verse fission of the cell, a fission preceded by a median 

 constriction. These are characteristics of the bac- 

 terium, strictly so called. 



The nutrition of this microbe resembles that oi 

 beer-yeast : it requires mineral salts, phosphates of the 

 alkaline metals and of the metals of the alkaline 

 earths, proteid matters, or ammoniacal salts. 



This ferment is an oxidizing ferment, which with- 

 draws oxygen from the air and transfers it to the 

 alcohol, thus converting it into acetic acid ; hence it 

 can only subsist in contact with the air, and perishes 

 when it is submerged, so that acetification is then 

 arrested. The oxidizing power of this microbe is 

 such that it can even oxidize alcohol and transform it 

 into carbonic acid gas a fact which explains how the 

 strength of wine is lowered by the other and larger 

 species, Mycoderma vini, of which we have given an 

 illustration (Figs. 43, 44). This action is less lively 

 in the presence of a considerable quantity of vinegar, 

 and at Orleans acetification is always effected in vats 

 which contain a large amount. 



What is called the Orleans process, which is the 

 one generally employed in France, consists in filling 

 tuns which can hold about 200 litres with 100 litres 

 of vinegar and 10 litres of white or red wine ; once a 

 week 10 litres of vinegar are drawn off, and replaced 

 by 10 litres of wine. The temperature should be 

 about 30. Oxygen is supplied by a proper system of 



