236 STUDIES ON FERMENTATION. 



natural saccharine juices, we may ask whether we must still 

 regard the reactions that occur in these fermentations as phe- 

 nomena inexplicable by the ordinary laws of chemistry. We 

 can readily see that fermentations occupy a special place in the 

 series of chemical and biological phenomena. What gives to 

 fermentations certain exceptional characters, of which we are 

 only now beginning to suspect the causes, is the mode of life 

 in the minute plants designated under the generic name of 

 ferments, a mode of life which is essentially diflferent from that 

 in other vegetables, and from which result phenomena equally 

 exceptional throughout the whole range of the chemistry of 

 livinw beings. 



The least reflection will suffice to convince us that the 

 alcoholic ferments must possess the faculty of vegetating and 

 performing their functions out of contact with air. Let us 

 consider, for instance, the method of vintage practised in the 

 Jura. The bunches are laid at the foot of the vine in a large 

 tub, and the grapes there stripped from them. When the 

 grapes, some of which are uninjured, others bruised, and all 

 moistened by the juice issuing from the latter, fill the tub — 

 where they form what is commonly called the vintage — they 

 are conveyed in barrels to large vessels fixed in cellars of a 

 considerable depth. These vessels are not filled to more than 

 three-quarters of their capacity. Fermentation soon takes 

 place in them, and the carbonic acid gas finds escape through 

 the bunghole, the diameter of which, in the case of the largest 

 vessels, is not more than ten or twelve centimetres (about 

 four inches). The wine is not drawn off before the end of two 

 or three months. In this way it seems highly probable that 

 the yeast which produces the wine under such conditions must 

 have developed, to a great extent at least, out of contact with 

 oxygen. No doubt oxygen is not entirely absent from the 

 first ; nay, its limited presence is even a necessity to the 

 manifestation of the phenomena which follow. The grapes are 

 stripped from the bunch in contact with air, and the must 

 which drops from the wounded fruit takes a little of this gas 



