STUDIES ON FERMENTATION. 193 



other to preponderate, and incline us to believe that a trans- 

 formation had really occurred. 



It is true that brewers generally are of a different opinion. 

 Most of them assert that '* low " yeast cultivated at a high 

 temperature becomes " high " yeast ; and conversely^ that 

 " high " yeast becomes " low " by repeated growths at a 

 low temperature. Many have told us that they have proved 

 this. Nevertheless it is our belief that the success of such 

 transformation lias been but apparent, attributable in each case 

 to the fact, as we have just stated, of their having operated 

 on a mixture of the two yeasts. 



Mitscherlich, and various authors after him, have asserted 

 that "high" yeast propagates by budding, and "low" yeast, 

 on the contrary, by spores, formed by the endogenous division of 

 the protoplasm of the cells, and set free by the rupture of the 

 cell- wall, which then, increasing in size, assume the character 

 of ordinary cells. But we have never been able to confirm this. 

 Fig. 41 represents a field of low yeast, taken from the 

 deposit in a vat after the fermentation of the beer was finished. 

 The granular matter mixed with the cells is altogether amor- 



Fig. 41. 



phous, although in many cases perfectly spherical. It is a 

 product in no way related to this yeast (see Plate I., No. 7).* 

 " High " yeast and all the ferments of beer have this kind 



* [A rather serious clerical error appears to have here crept into the 

 origiual, for on referring to Plate I. and the letterpress descriptive of No. 7 

 (p. 5), we find it applies to a very formidable species of diseased fer- 

 ment, whereas the author is here speaking of an amorphous deposit, 

 harmless in character, and more or less associated with all yeasts. 

 Doubtless No. 7 should stand No. 6, see p. 6. — D. C. E.] 



o 



