STUDIES ON FERMENTATION. 159 



of yeast. This readily developed, and promptly produced 

 fermentation.* 



It seems possible, therefore, that the germs of ferment may 

 not exist on bunches of sound grapes during winter, and that 

 the well-known experiment of Gay-Lussac on the influence 

 of air on the fermentation of the must of crushed grapes 

 cannot succeed at all times. 



The following observations will aSbrd more than sufiicient 

 proof of this statement, being, after all, but an easy method 

 of carrying out Gay-Lussac's experiment, without having 

 recourse to the use of mercury. 



It may already be inferred from the preceding facts that 

 there must be, in the course of the year, between the end of 

 winter and autumn, a period when the vegetation of the cellules 

 from which yeast proceeds undergoes a revival. When does 

 this period occur ? In other words, how long after winter does 

 sterility of the plant continue, until it is again capable of yield- 

 ing ferment? To ascertain this, we conducted numerous experi- 

 ments during the summer and autumn of 1875 and the winter 

 of 1876. Having to conduct them in a vine-growing country 

 — in the vineyards of Arbois, Franche-Comte — at a distance 

 from our laboratory, we were compelled to adopt a simple form 



* In experiments of this kind there is always a slight increase in the 

 volume of air in the jar. This increase may be very perceptible even 

 when the experiment made with fresh grapes, in August, for instance, 

 causes no fermentation due to the action of yeast. After the oxygen 

 of the air has been absorbed and replaced by carbonic acid gas, either by 

 direct oxidation or by the action of moulds, the grapes, although crushed, 

 act like fruits plunged into carbonic acid gas {a), and this effect is even more 

 marked in the case of imperfectly crushed grapes. The reason is, that the 

 crushing is never so perfect as to injure all the cells of the parenchyma. 

 We may easily convince ourselves that the experiment on the liberation of 

 carbonic acid gas and the formation of alcohol by grapes and fi-uits in 

 general when plunged into carbonic acid succeeds very well in the case of 

 fragments of fruits or grapes, and succeeds better the less the parts are 

 crushed. 



(a) Spe paragraph : Fermentation in saccharin? fruits immersed in carbonic acid gas, 

 Chap, vi , § 2, p. 266. 



