248 STUDIES ox FERMENTATIOX 



veloped with much difficulty, by reason of the conditions to which 

 it had been subjected. In appearance the cells varied much, some 

 were to be found large, elongated, and of tubular aspect, some 

 seemed very old and were extremely granular, whilst others were 

 more transparent. All of them might be considered abnormal cells. 



In such experiments we encounter another difficulty. If the 

 yeast sown in the non -aerated fermentable liquid is in the least 

 degree impure, especially if we use sweetened yeast-water, we 

 may be sure that alcoholic fermentation will soon cease, if, 

 indeed, it ever commences, and that accessory fermentations will 

 go on. The vibrios of butyric fermentation, for instance, will 

 propagate with remarkable facility under these circumstances. 

 Clearly then, the purity of the yeast at the moment of impreg- 

 nation, and the purity of the liquid in the funnel, are conditions 

 indispensable to success. 



To secure the latter of these conditions, we close the funnel, 

 as shown in Fig. 60, by means of a cork pierced with two holes, 

 through one of which a short tube passes, to which a short 

 length of india-rubber tubing provided with a glass stopper is 

 attached; through the other hole a thin cui^ved tube is passed. 

 Thus fitted, the funnel can answer the same purposes as our 

 double-necked flasks. A few cubic centimetres of sweetened 

 veast- water are then put in it and boiled, so that the steam may 

 destroy any germs adhering to the sides. When cold the liquid 

 is impregnated by means of a trace of pure yeast, introduced 

 through the glass-stoppered tube. If these precautions are 

 neglected it is scarcely possible to secure a successful fermenta- 

 tion in our flasks, because the yeast sown is immediately held in 

 check by a development of anaerobian vibrios. For greater 

 security, we may add to the fermentable liquid, at the moment 

 when it is prepared, a very small quantity of tartaric acid, 

 which will prevent the development of but3'ric vibrios. 



The variation of the ratio between the weight of the yeast 

 and that of the sugar decomposed by it now claims special atten- 

 tion. Side by side with the experiments which we have just 

 described, we conducted a third lot by means of the flask C 



