MICROBES, OE BACTERIA. 97 



ventilation. This process is somewhat slow, since it 

 only produces ten litres of vinegar out of each tun in 

 the course of the week, and it has the disadvantage 

 of encouraging the multiplication of anguillidce, the 

 small nematoid worms which live in vinegar and sour 

 paste. 



Pasteur has modified and improved the original 

 process so as to obviate both inconveniences. He 

 employs heat, which allows the process of acetification 

 to be intermittent, and thus prevents the development 

 of the anguillidce. Shallow vats, about 30 centi- 

 metres in depth, with lids in which holes have been 

 pierced, are used, and mycoderma is scattered on their 

 surface. Gutta-percha tubes, pierced with holes at 

 their lower extremity, are placed at the bottom of 

 these vats, so that fresh liquid can be added without 

 disturbing the superficial film of mycoderma. 



In Germany, vinegar is made by means of spongy 

 platinum, or platinum black, which oxidizes alcohol 

 without the intervention of a microbe. This affords 

 a good example of fermentation, or of an analogous 

 phenomenon, produced solely by physico-chemical 

 action. The platinum black acts by disintegrating 

 the alcohol and placing it in more intimate contact 

 with the oxgyen of the air, since the process of 

 oxidation would be much slower without either this 

 process or the presence of the ferment. 



