CHAPTER XVII 



YEAST FUNGI : TORULACE^, SACCHAROMYCES 



Yeast, iorula (Pasteur), or saccharomyces, is not a bac- 

 terium, but belongs to an altogether different order of fungi 

 — the Blastomycetes. It consists of spherical or oval cells, 

 very much larger than the largest micrococci, and as in the 

 case of these each cell consists of a membrane and contents. 

 The contents are either homogeneous or finely granular proto- 

 plasm ; in the latter case there are generally present one, 

 two, or more small vacuoles. 



There are a great many species of Tonila, varying from 

 one another morphologically chiefly in their size, and 

 physiologically by their action on various fluids (see below). 



The cells multiply in suitable media by gemmation, a 

 minute knob-like projection appearing at one side of the cell, 

 and enlarging till it reaches nearly the size of the original or 

 mother-cell. It finally becomes altogether constricted off 

 from this latter, or having reached its full size remains 

 fixed to the mother-cell, and each cell again producing 

 by gemmation a new cell. In this way aggregations 

 of four, six, eight, or more cells are formed, which may 

 be arranged either as a chain when the production proceeds 



