184 



MICRO-ORGANISMS AND FERMENTATION. 



As examples of two different bottom-fermentation species 

 of yeast, the Carlsberg bottom-yeasts " No. 1 " (Fig. 48) and 

 " No. 2 " (Fig. 49) employed in the Old Carlsberg brewery at 



FIG. 48. 

 Carlsberg bottom-yeast No. 1, after Hansen. 



Copenhagen, may be more minutely described. Distinct 

 differences are noticeable even in the ordinary microscopic 

 examination. 



The cells of the species No. 1 (Fig. 48) are mostly some- 

 what elongated, but there are also smaller characteristic 



FIG. 49. 

 Carlsberg bottom-yeast No. 2, some cells with spores, after Hansen. 



pointed cells. When the yeast taken from the fermen ting- 

 vessel is washed with water and placed for a short time under 

 ice, the contents of all the cells will quickly assume a granular 

 appearance, and if the yeast is kept in this manner for 

 several days the number of dead cells will very rapidly increase. 

 The cells of the species No. 2 are, under normal conditions, 

 roundish oval, some being almost spherical. Here and there 

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



