i;8 "DISEASES" OF BEER, 



Few works have on their first appearance attracted as 

 much attention as Nageli's book on the lower fungi.* The 

 influence which it exerted did not, however, correspond with 

 the expectations which it raised, as many of the statements 

 which it contained were wanting in proof. With regard to 

 the Saccharomycetes and bacteria, Nageli expresses on pp. 

 20-22 the view that the species are able to undergo rapid and 

 abundant variation, both in their morphological and physio- 

 logical properties, and that many of the forms can be readily 

 converted one into the other. Also, with regard to the 

 special fermentative activity which one form may possess, he 



yeast (verwilderte Hefe). The authors describe no scientific experiments, and 

 believe that they are able to settle the matter by a microscopic examination ; they 

 cause great confusion, but they add no information. They might with profit 

 study the above-mentioned treatise of the famous old zymotechnologist. 



The terms "light yeast" and "degenerated" yeast, as employed in this litera- 

 ture, imply two very different things. Sometimes, as Lintner's observations show, 

 they are only taken to imply cells which have an unsatisfactory appearance under 

 the microscope, but nevertheless give a good result in the brewery. Sometimes, 

 on the other hand, cells are meant which have suffered some change which makes 

 them less suited to carry out the work desired by the brewer. In my various 

 treatises, from 1883 to the present time, observations occur here and there which 

 have reference to these two cases, and I hope later to be able to publish a more 

 extensive experimental investigation in this direction. The question relating to 

 the laws affecting the variation of species of yeast is a very complicated one. If 

 the authors, to whom I here refer, had studied my investigations with some degree 

 of thoroughness, and especially those which I have published during the last years, 

 they would have perceived that especially in this field it requires great labour to 

 achieve only modest results, and that a great deal more has to be accomplished 

 before we can really think of establishing theories of general applicability. They 

 would then also know that it is not possible by means of a microscopic examina- 

 tion of a yeast cell to judge how it will behave in the brewery. And if they had 

 carried out experiments such as those conducted by myself and my pupils, they 

 would have learnt that the cells, which from their standpoint they describe as 

 large and satisfactory, will in many cases produce a yeast which the brewer has to 

 reject, whilst inversely their so-called "light" and "degenerated" yeast cells are 

 often good vigorous cells which in the brewery develop a good yeast. If the 

 authors to whom my advice is directed could be converted, they would take up a 

 more modest position with regard to the difficult problems mentioned, and they 

 would in the future write less but make more experiments. I heartily wish that 

 this might happen, for the half-scientific literature has always been, and is still, 

 a source of mischief for zymotechnic science. 



* Nageli, ' Die niederen Pilze in ihren Be/iehungen zu den Infektionskrank- 

 heiten und der Gesundheitspflege,' Munich, 1877. 



