RESEARCHES ON YEASTS. 85 



visia /., was, in 1882, the chief constituent of a yeast largely 

 employed in Edinburgh and London breweries ; it is not im- 

 probable that this yeast still plays an important part in those 

 breweries, but I have not since made any exact experiments 

 on this point. Besides this species there are other high-fer- 

 mentation culture yeasts in English and Scotch breweries, 

 and different species are also employed in Danish breweries. 



3. INVESTIGATIONS ON LOW-FERMENTATION YEASTS 



WHICH HAVE BEEN TESTED IN PRACTICE. 



From the way in which my above investigations de- 

 veloped, it became necessary to examine first the wild yeasts, 

 and especially those which produce sickness in beer, and then 

 the low-fermentation culture yeasts. On account of the small 

 importance of high fermentation in Denmark, and in most 

 other brewing countries, less attention was paid to the yeasts 

 employed in this branch of the industry, and only in the case 

 of Sacch. cerevisice I. was a thorough systematic investigation 

 carried out. 



In 1881 I expressed the view in one of my papers that the 

 low-fermentation yeast employed in breweries consisted of 

 only one species Sacch. cerevisics ; at that time this was the 

 general opinion. The differences which the yeast exhibited 

 were attributed essentially to local circumstances, and it was 

 thought that these differences were easily interchangeable, 

 and could again disappear. It gradually became the custom 

 to speak of Sacch. cerevisice as of a definite and well-known 

 quantity, and this was also done in the publications from the 

 Carlsberg Laboratory up to the end of 1881. I was then for 

 the first time able to submit the question to an experimental 

 treatment. I thereby soon gained a very different insight 

 into the matter, and the main result proved that the view 

 which had been held with regard to the systematic name Sacch. 

 cerevisice (low-fermentation form) was incorrect ; for under 



