314 APPLIED BACTERIOLOGY 



The spore-forming cells are larger (7 to 8'5 /j,), and contain 

 from two to four spores 3'5 fi in diameter. This yeast 

 is stated by Engel to be identical with that employed by 

 bakers to ferment bread. 



Saccharomyces Exiguus. — Conical or top-shaped cells 5 /j, 

 long, and reaching 2*5 /u, in thickness, in slightly branching 

 colonies. There are two to three spores in a row in each 

 m'other-cell. This yeast is often present in the after- 

 fermentation of beer. 



Torulae. — The terni torula has been used both by Pasteur 

 and Hansen to denote a number of organisms closely re- 

 lated to the saccharomycetes in their form and mode of 

 growth, but differing from them in not giving rise to spores 

 even when cultivated under the most diverse conditions. 

 The torulm produce little or no alcohol when grown in 

 saccharine liquids. To this group belong the Saccharo- 

 myces rosaceus, niger, and albus, the pink, black, and white 

 torula respectively that are frequently met with in the air. 



Examination of Yeasts. — Hansen, to whom the present 

 scientific aspect of the fermentation industries is due, 

 elaborated a scheme for the examination of the saccharo- 

 mycetes, which depends upon the isolation of a pure 

 culture, and the observation of the temperature and time 

 they take to form ' ascospores ' and ' films.' 



The importance of this method of investigation will be 

 apparent when applied to the examination of brewery yeast 

 to determine the presence of disease or ' wild ' yeasts, which 

 are the cause of such diseases as muddiness, ropiness, 

 bitter or acid taste, which render the beer undrinkable, or 

 injure its keeping properties. Starting with pure yeast, 

 thorough cleanliness, and means of keeping the beer free 

 from ' wild ' yeasts and other organisms, beer may be pre- 

 served both bright and clear, even though the temperature 

 be comparatively high. To obtain pure yeasts, it is first 



