218 



OUTLINES OF BACTERIOLOGY 



investigated as a pure culture, the conditions determining its optimum 

 growth became known. It is therefore obvious that if must be 

 inoculated with a pure culture of this species, and allowed to 

 ferment under conditions most favourable to its growth, the chances 

 of a good result are much greater than when the fermentation is left 

 to chance. 



Saccharomyces ellipsoideus I. is only one of many yeasts concerned 

 in wine-fermentation. In experimental stations for wine culture 

 numerous species related to Saccharomyces ellipsoideus I. have been 

 isolated. Among the best known is " Johannisberg II.," which has 

 the peculiarity that when cultivated on gypsum blocks (the recognised 

 method for the production of spores in yeast cells) as many as 99-100 

 per cent, of the individuals develop spores. 



The following table gives the percentage of alcohol in the best-known 

 wines : 



The diseases which wines are liable to contract, arise as a result of 

 fermentations set up by certain bacteria which have gained entrance 



Fia. 123. — Bacterium aceti. 

 (Aftei- Hansen.) 



ff 









qOO 

 , On 



Ifi 



Fig. 124.— Bacterium Pastorianum. 

 (After Hansen.) 



into the wines. These bacteria produce obnoxious substances, which 

 render the wine highly unpalatable. The number of harmful bacteria, 

 however, is very small, because for most bacteria wine as a nutrient 



