WHAT IS THE PURE YEAST OF PASTEUR? 147 



method which Velten gave in 1878 there is not a word to the 

 effect that the cultivation should be conducted at a low 

 temperature, and neither does any such statement occur in 

 the works of Pasteur and Duclaux. Velten has only 

 words to bring forward ; he has no proof and no experi- 

 ments. My colleague, Mr. Jorgensen, has published a sharp 

 rejoinder to Velten's assertions in ' La Gazette du Brasseur ' 

 (1891, No. 215), and in the 'Allgemeine Brauer- and Hop- 

 fenzeitung,' Nuremberg (1891, No. 142). In this Jorgensen 

 gives the following account of his own experience : 



" Eleven years ago, when the Tuborg brewery at Copen- 

 hagen was suffering from a very pronounced yeast turbidity 

 of the beer, and which was produced by wild yeasts, I made 

 use of Pasteur's method for purifying the yeast on a large scale, 

 the yeast being treated with the tartaric acid solutions in 

 vats of 5 to 6 hectoliters capacity in the fermenting cellar, 

 and at the temperature employed in low fermentation. No 

 improvement whatever was obtained, the disease always 

 occurred again, and only disappeared when a true pure yeast 

 was introduced in accordance with Hansen's method in the 

 place of the yeast purified by tartaric acid. It may further be 

 stated that during the last half year a large number of experi- 

 ments have been made in my laboratory with mixtures of 

 culture yeasts with widely differing amounts of the various 

 wild yeasts, and amongst the latter disease yeasts, these mix- 

 tures being cultivated in wort containing about o * 5 per cent, 

 of tartaric acid. It has always been found that the wild 

 yeasts gradually developed at the expense of the culture 

 yeast, and that the latter became completely suppressed. It 

 is thus shown that the addition of tartaric acid to the wort 

 also fails to effect any purification, but rather that it favours 

 the development of disease yeasts." 



In order to, if possible, silence my opponents, and to 

 thoroughly investigate the question, I carried out the follow- 

 ing experiments, in which low temperatures were employed, 



L 2 



