SYSTEMATICALLY SELECTED YEASTS. 15 



had led to a striking result in practice, and this tended in a 

 high degree to support the correctness of my doctrine con- 

 cerning the Saccharomycetes. In a treatise on the diseases 

 of beer, I had explained the cause of the malady, namely 

 yeast turbidity, which had produced such disastrous results 

 for two years in the Tuborg brewery at Copenhagen, and as 

 matters rapidly mended when the explanation given was 

 acted upon, substantial proof was afforded of the practical 

 value of my discoveries. At about the same time a difficulty 

 occurred in Jacobsen's brewery, namely, the beer began to 

 acquire a disagreeable bitter taste and an unpleasant odour. 

 In accordance with the views then prevailing, he naturally 

 attributed the malady to bacterial contamination, and when 

 it was found that bacteria could not be detected, he assumed 

 that the wort and especially the hops were at fault. Here 

 again, however, nothing wrong could be discovered. In a 

 treatise published in 1882, I incidentally gave an account of 

 the investigation of a Saccharomyces which gave a similar 

 beer to that complained of in Old Carlsberg. I at once 

 expressed the opinion that wild yeasts can produce equally 

 serious disturbances in the fermentation industry as are 

 caused by bacteria. It is natural that no great attention 

 was paid to my doctrine at that time, for it was not then 

 sufficiently established. In 1883, however, I made another 

 step in advance, and it was through the success which I had 

 met with in the Tuborg brewery that the desired permission 

 was granted me. The experiments were, therefore, carried 

 out on a large scale in the brewery, and irrefutable proofs 

 were gradually furnished. 



From the impure yeasts I separated four Saccharomycetes, 

 and on experimenting partly with each separately and partly 

 with mixtures, it was found that only one of them gave a 

 normal beer of good flavour and odour. This is the species 

 which is now generally known in the brewing world as 

 Carlsberg bottom yeast, No. I. That this species is in itself 



