112 MORPHOLOGY AND LIFE-HISTORY OF YEASTS. 



strictest sense the term is applied to such budding fungi as are 

 capable of exciting alcoholic fermentation, and therefore the 

 alcohpl-producing Mucors are not to be classed as yeast ; neither 

 are the Saccharouu/eetes tliat lack fermentative power. Even in 

 Pasteur's (III.) " Studies on Beer " no mutual limitation is 

 placed on the terms Saccliaromnces and yeast, but both are 

 regarded as interchangeable, so that in many places we are 

 unable to ascertain which is meant. The chief interest attach- 

 ing to the yeasts is in respect of their practical utility. In 

 many treatises on the physiology of the ferments the question 

 whether they should be considered as Sairharotnycetes, or as 

 budding fungi of some other species, is left untouched. It is 

 therefore impracticable to relegate the species there mentioned 

 to one or the other group ; and in such cases there remains no 

 alternative but to speak generally of " yeast." This has also 

 been done, and should be so understood, in the following para- 

 graphs. 



In laboratories where pure yeasts are cultivated for the pur- 

 poses of the practical fermentation industry, it is very seldom 

 that the rules of scientific nomenclatvire are adopted by sup- 

 plementing the term Sarcharomyces with a specific name, even 

 when the species of the organism is known with certainty, the 

 usual practice being to name the yeast in accordance with the 

 locality of origin. Thus the Johannisberg wine yeast No. i, 

 illustrated in Fig. 124, was obtained from the sediment of a 

 young Johannisberg wine. " Saaz yeast " is a bottom-fermen- 

 tation beer yeast isolated by P. Lindner from the stock yeast of 

 the Saaz brewery (Bohemia). This yeast will be frequently 

 mentioned later, on account of its very low power of attenuation. 

 The very high-attenuation " Frohberg yeast" originated at 

 Frohberg's brewery, Grimma (Saxony). In many instances the 

 yeast is simply given a number, under which it is registered in 

 the laboratory collection (living herbarium) and is cultivated 

 further. Thus, the distillery yeast known to distillery techno- 

 logists and mycologists under the abbreviated title "Race II.," 

 is the second of a series of yeasts given out by the Berlin 

 Experimental Station, for practical testing in respect of their 

 utility, the species in question finally proving superior to the 

 others. 



It may be remarked casually that a proper discrimination 

 between the three expressions : budding fungus, Saccliaromyces, 

 and yeast, is often lacking in medical treatises dealing with a 

 pathogenic budding fungus. Some of these are known to pro- 

 duce illness, even attended with fatal results, when they find 

 the conditions of development favourable in the body in which 

 they have made their habitat. The literature on this matter 

 has been collected by J. Raum (I.), and in a monograph by 

 O. BussE (I.), as also in the different volumes of P. Baum- 



