240 CHEMICAL INFLUENCES ON YEAST. 



12-12.5 per cent, of alcohol in the nutrient medium. This 

 discovery, which was made chiefly in connection with German and 

 Swiss wine yeasts, was afterwards extended and confirmed by the 

 researches of C. Form (I.) on Italian wine yeasts. In investigating 

 the preparation of the rice spirit, Awamori, in the Loochoo Islands, 

 near Formosa, INUI (I.) described a yeast, Sacch. Awamori, which 

 plays an active part in the process, and whose development is not 

 crippled until the medium contains 13 per cent, of alcohol, 20 per 

 cent, being required to arrest it completely. The Sake yeast 

 examined by K. YABE (II.) continues to grow until the alcohol 

 content of the medium attains 24 percent. Afar lower power of 

 resistance is exhibited by two red budding fungi discovered by 

 YABE (I V.) in the air of Japan and on the surface of rice straw, to 

 which he gave the hardly appropriate names, Saccharomyces Japo- 

 nicus&nd S. Keiskeana. The development of both these organisms 

 is checked by 7 per cent, of alcohol in the medium. The budding 

 fungi described by RICHARD MEISSNER (II.), which are incapable 

 of forming alcohol and therefore do not belong to the yeasts, 

 though they are of technical importance on account of their power 

 of turning must and wine ropy (see p. 177), cease to reproduce 

 and to form mucus when the medium contains over 5 per cent, 

 (vol.) of alcohol. 



Under otherwise equal conditions a larger quantity of alcohol 

 is necessary to check fermentative activity than to stop repro- 

 duction. Thus a pressed yeast examined by HAYDUCK (IV.) was 

 able to set up active fermentation in a saccharose nutrient salt 

 solution containing 7 per cent, of alcohol, though not to reproduce 

 therein. According to the researches of BREFELD (XV.), the 

 addition of 17.3 per cent, of alcohol to the nutrient solution is 

 necessary for preventing fermentation, though in HAYDUCK'S ex- 

 periments (III.) this result ensued in presence of 15 per cent, of 

 alcohol. U. PEGLION (II.) found a yeast still actively engaged in 

 the secondary fermentation of an Italian wine containing 14.3 per 

 cent, of alcohol. Further reports on the influencing of alcoholic 

 fermentation by the presence of alcohol will be found in chapter Ixiii., 

 and the same point in connection with Mycoderma is discussed in 

 chapter Ix. 



Temperature is the first of the external conditions exercising a 

 determinating influence on the amount of alcohol required to 

 restrict fermentation. This influence is progressive as the tem- 

 perature rises within the limits that can be taken into consideration. 

 In the first place, the rise in temperature is accompanied by a 

 greater physical permeability of the cell membrane for the osmotic 

 conveyance of alcohol into the cell ; and, secondly, by the physio- 

 logical mobility of the molecular groups of the plasma, and 

 consequently the sensitiveness of this substance to external influ- 

 ences. For definite information on this point we are indebted to 

 H. MIJLLER-THURGAU (XIV.), who found that, under otherwise 



