ALCOHOLIC FERMENTS. 221 



Distinct differences are noticeable even in an ordinary micro- 

 scopic examination. The cells of species No. 1 (Fig. 69) are 

 mostly somewhat elongated, but there are also smaller, 

 characteristic, pointed cells. When the yeast taken from the 

 fermenting-vessel is washed with water and placed for a short 

 time under ice, the contents of all the cells quickly assume a 

 granular appearance, and if the yeast is kept in this way for 

 several days the number of dead cells will very rapidly 

 increase. The cells of species No. 2 are, under normal con- 

 ditions, roundish oval, some being almost spherical. Here and 

 there giant-cells occur (left-hand side of figure). In a yeast- 

 mass washed with water the cell-contents long remain clear, 

 and only slightly granular, and if the yeast be kept for a long 

 time in this way very few dead cells will be found. 



The gelatine cultures of both species form colonies, having 

 the ordinary appearance of the Saccharomycetes. 



On gypsum blocks the species No. 2 develops spores much 

 more quickly and abundantly than No. 1 species. 



The fermentation phenomena also differ. No. 2 gives thick, 

 high foam and a dense, firm layer on the surface ; No. 1 gives 

 a low foam, the liquor being often exposed in places. No. 2 

 clarifies comparatively quickly ; No. 1 clarifies slowly. No. 2 

 forms a firm layer at the bottom of the fermenting-vessel, while 

 No. 1 gives a fluid sediment. In the primary and secondary 

 fermentations No. 2 gives a more feeble fermentation than 

 No. 1. 



The finished beer obtained in the same brewery with the 

 two yeasts shows marked differences. With regard to taste, 

 the beer obtained with No. 2 yeast is preferred by most, but 

 this is a matter of opinion ; at all events the taste is different 

 in the two cases. Finally the two species give very different 

 results as to the stability of the beers with regard to yeast 

 turbidity. The beer prepared with No. 1 yeast is decidedly 

 more stable in this respect than that prepared with No. 2 

 yeast. Consequently No. 1 is especially suited for lager and 

 export beers, and No. 2 for running beers. These character- 

 istics have been found to remain unchanged for years. 

 (Compare BORGMANN'S work on the chemical action of the two 

 species.) 



