PRODUCED BY ALCOHOLIC FERMENTS. 185 



already stated, the view which was the most widely held, was 

 that deep-seated transformations in a good brewery yeast can 

 readily occur in practice, a view which gave rise to much 

 discussion about the degeneration of yeast ; no experiments, 

 however, were undertaken in support of this view. 



In my treatise, which was published in 1879, I took up 

 essentially the same standpoint ; after carefully considering 

 the question, however, I soon perceived that it would be 

 useless to continue the discussions of my predecessors, but 

 that decisive experiments were necessary, and that, until the 

 latter had been made, it would be best to remain silent. 

 Several years were spent on the preliminary work. First of 

 all it was necessary to elaborate a method of pure cultivation, 

 in order that I might know with perfect certainty whether I 

 was working with one or with several species. I therefore 

 took as my starting-point the individual, the single cell. My 

 next problem was to discover characters which would enable 

 me to solve the intricate questions of species, race, and variety. 

 I have, in the course of some years, treated these problems 

 from different points of view. The first characters which I 

 found related to the development of spores, with especial 

 reference to the cardinal points of temperature. It is now 

 generally acknowledged that this method of spore analysis is 

 of importance, and on this basis I have further devised the 

 above-mentioned method for the practical examination of 

 brewery yeast. I therefore still lay great weight on these 

 characters ; but I have never held the opinion as often stated 

 by superficial readers of my writings that they are, in them- 

 selves, sufficient for the determination of all species ; on the 

 contrary, I have always endeavoured to discover new distinc- 

 tive characters, and I have also already given a whole series. 



In 1882 and 1883, two exceptionally favourable oppor- 

 tunities occurred for testing the applicability of my new 

 weapons in practice. I refer to the maladies with which 

 the Tuborg and Old Carlsberg breweries were at that time 



