STUDIES ON FERMENTATION. 229 



raw yeast in a flask of sweetened water. On the 24tli we 

 poured off the liquid, and supplied the deposit with fresh 

 sweetened water. The exterior temperature was 12° C. (54° 

 F.). On the 27th we took some of the deposit and put it 

 into a flask of wort. The following days there was a develop- 

 ment of yeast, accompanied by fermentation. We obtained, 

 however, neither the large forms of the ferments of fruits, 

 nor those of the more minute ferments represented in Plate XI. 

 The saccharomyces pastorianus, represented in the yeast which 

 we sowed by aged, granular, elongated cells, had, therefore, 

 not revived. Fearing that this result might have been 

 attributable to insufiiciency of the exhaustion, which had only 

 lasted for a few days, we raised the temperature of the flask 

 of sweetened water to 25° C. (77° F.), at which we kept it until 

 February 20th. On that day we sowed some of this yeast in 

 wort. There was a very perceptible revival the next day, but 

 it was still impossible to detect with the microscope the forms 

 we have just mentioned, nor did saccliaromyces pastorianus 

 appear in fresh, succeeding growths. 



Fig. 58 represents the yeast formed, which evidently had 



Fig. 58. 



sprung from the transparent cells seen in Fig. 57, and 

 doubtless belonging to the ordinary ferment of wine, saccha- 

 romyces ellipsoideus. Here we have another example of the 

 natural separation of ferments brought about by the death 

 of one or two of them, or by extreme difierences in the time 

 of their revival. 



