266 STUDIES ON FERMENTATION. 



pouriug some wort on the deposit of the plant, which remained 

 in the flask. In less than five hours from the time when we 

 placed it in the oven, the plant had started fermentation in the 

 wort, as we could see by the bubbles of gas rising to form 

 patches on the surface of the liquid. We may add that yeast 

 in the medium which we have been discussing will not develop 

 at all without air. 



The importance of these results can escape no one ; they 

 prove clearly that the fermentative character is not an invariable 

 phenomenon of yeast-life, they show that j'east is a plant which 

 does not differ from ordinary plants, and which manifests its fer- 

 mentative power solel}^ in consequence of particular conditions 

 under which it is compelled to live. It may carry on its life as 

 a ferment or not, and after having lived without manifesting the 

 slightest symptom of fermentative character, it is quite ready to 

 manifest that character when brought under suitable conditions. 

 The fermentative property, therefore, is not a power peculiar to 

 cells of a special nature. It is not a permanent character of a 

 particular structure, like, for instance, the property of acidity or 

 alkalinity. It is a peculiarity dependent on external circum- 

 stances and on the nutritive conditions of the organism. 



§ II.— Fermentation in Saccharine Fruits Immersed 

 IX Carbonic Acid Gas. 



The theory which we have, step by step, evolved, on the 

 subject of the causes of the chemical phenomena of fermenta- 

 tion, may claim a character of simplicity and generality that is 

 well worthy of attention. Fermentation is no longer one of 

 those isolated and mysterious phenomena which do not admit 

 of explanation. It is the consequence of a peculiar vital pro- 

 cess of nutrition which occurs under certain conditions, differing 

 from those which characterize the life of all ordinary beings, 

 animal or vegetable, but by which the latter may be affected, 

 more or less, in a way which brings them, to some extent. 



