RESEARCHES ON YEASTS. 89 



We will now proceed to describe how the two yeasts 

 behave in the brewery. The experiments were conducted 



were well known through several years' trial in different breweries. Two of them 

 gave a feeble attenuation, two gave a strong attenuation, and it was stated that, 

 as regards fermentation, the last two occupied an intermediate position between 

 the above. The differences between these species revealed by a careful micro- 

 scopic examination were, however, ill-defined, and not of the nature which I have 

 described in the case of the two Carlsberg yeasts. Thus no rule of general 

 application was found, and the result showed that species of low attenuating 

 properties presented the same microscopic appearance as highly attenuative 

 yeasts. 



We all know that none of the theories of fermentation hitherto brought 

 forward by Stahl, Liebig, Pasteur, Nageli and others can explain the numerous 

 and very varied phenomena with which we are now acquainted ; the knowledge 

 which we possess has proved these theories to be incorrect, but is not yet able to 

 supply a true theory. Although these erroneous theories are, as a rule, still discussed 

 even in the text-books written for practical brewers, the main reason is, no doubt, 

 that the writers have thoughtlessly followed the same old beaten track. In 

 practice nothing is learnt from these speculations, and they are only of historical 

 interest. There can be no doubt but that the study of protoplasm will lead to 

 the solution of this important question, which will some day not only enrich 

 science, but will also prove of service in practice. In my investigations on the 

 behaviour of the alcoholic ferments towards the carbohydrates, I referred to the 

 yeast cell as a favourable subject for such investigations, and I have myself done 

 some work in connection with this problem. But nothing will be gained by a 

 simple microscopic examination like that mentioned above ; the attack must be 

 directed against the elementary parts of the protoplasm and the cell- wall ; our 

 object must be to find an expression for the functions in the structure and com- 

 position of the cell. 



It is only in the most recent times that it has been possible, with the help of 

 the highly-developed technique of modern science (microscopical, chemical and 

 physical), to make even a beginning in such investigations, and so far we have 

 not many results of general importance to chronicle in this field. With regard to 

 the fundamental problems touched upon above, it must even be confessed that 

 nothing has been accomplished. I refer here to the truly scientific investigations ; if, 

 however, we look through the half-scientific literature of some of the zymotechnic 

 journals for the last ten years, we shall find not a few publications in which it is 

 announced that these questions have been solved by the various authors. They 

 state how they have been able, by a simple microscopic examination of the yeast 

 cells, to foretell the behaviour of the yeast in the brewery, and likewise the attenua- 

 tion, the brightening, taste, stability of the beer, &c. &c. Investigators of this 

 kind do not, in their ignorance, in the least perceive the difficulties which others 

 continually encounter, and as they have no idea of the amount of work already 

 accomplished by such investigators as Strassburger, Wiesner, Zacharias, Flemming, 

 Zimmermann, F. Schwarz, Pfeffer, Schmitz, and several others, they ignore the 

 whole of the literature and boldly bring forward their own " discoveries." 



These half-scientific writings cause great confusion and do much harm. The 

 above remarks are directed as words of warning against this class of literature. 



