154 MICRO-ORGANISMS AND FERMENTATION. 



about the same time as wild yeast at the above temperature, 

 but at a temperature of 1 5 C. the cells of wild yeast show 

 spore-formation considerably sooner than the cells of these 

 cultivated yeasts. 



The cultures maintained at 250. are examined after an 

 interval of 40 hours, and those maintained at 15C. after an 

 interval of three days. 



Experiments made by the author show that high brewery- 

 yeasts can be analysed in a similar manner. In the case of 

 some species, however, the analysis is best made at 10-12 C., 

 because a well-marked difference of time between the beginning 

 of spore-formation in culture-yeast on the one hand and wild 

 yeast on the other is only observable at this temperature. 



According to the author's researches, distillers yeast may be 

 analysed in the same manner. Eather low temperatures are 

 usually preferable for this analysis. Often, however, the 

 investigation into the construction of the spore in the selected 

 yeast-type must form the chief part of the analysis, the 

 difference of time for spore-formation in culture-yeast and 

 wild yeast respectively frequently proving inadequate. 



Wine yeast, like beer yeast, may be analysed by HANSEN'S 

 method, as ADERHOLD has, more especially, emphasised. 



By means of experiments undertaken to determine to what 

 extent HANSEN'S analytical method can be relied on for 

 technical purposes in low-fermentation breweries, HOLM and 

 POULSEN concluded that a very small admixture of wild yeast, 

 about 1-200^ of the entire mass (Carlsberg bottom-yeast No. 

 1), can be detected with certainty in t/iis manner. HANSEN'S 

 previous researches had shown that when, for instance, the two 

 species, Sacch. Pastorianus III. and Sacch. ellipsoideus II., 

 which are capable of producing yeast- turbidity in beer are 

 present to the extent of only 1 part in 41 of the pitching- 

 yeast, the disease is not developed, provided that the normal 

 conditions of fermentation and storage have been maintained. 

 Further, Sacch. Pastorianus I., which imparts to beer a dis- 

 agreeable odour and an unpleasant bitter taste, can, under the 

 same conditions, scarcely exert its injurious influence when the 

 admixture of this yeast amounts to less than 1 part in 22 of 

 the pitching-yeast. Consequently, HANSEN'S method for the 



