PRODUCED BY ALCOHOLIC FERMENTS. 171 



and to the dangers which these may be able to bring 

 about. 



Since then, brief accounts by different authors having 

 reference to Sacch. exiguus have frequently appeared in the 

 brewing journals ; these, however, contained nothing new, and 

 may here be passed over. With regard to my own investi- 

 gations in connection with this species, I refer the reader to 

 the account on subsequent pages. 



It was imagined that this small yeast fungus was to be 

 found in all cases where anything was wrong with the beer, 

 and as a starting-point it was always erroneously assumed 

 that this species could be detected with certainty with the 

 help of the microscope. Engel* also took this view of the 

 question. The well-known brewer, Gruber, of Strasbourg, had 

 noticed that his beer became attacked by a characterietic 

 disease after it had been six to nine months in the lager 

 casks. In this disease a new fermentation set in which 

 rendered the beer opalescent and gave it a greenish hue. 

 When this fermentation ceased, the beer became bright, but 

 in the place of its original good fresh taste, it had acquired a 

 vinous flavour. On examining this beer under the microscope, 

 Engel found numerous small yeast cells, which, in accordance 

 with the custom of the day, he, without hesitation, stated to 

 be Sacch. exigims^ and he likewise expressed the opinion that 

 the after-fermentation in question must have been produced 

 by these cells. At that time investigations were carried 

 out rapidly, and the results were in accordance with the 

 methods. 



A view, which was also advanced at that time was that 

 each of the various kinds of wine and beer had its own 

 species of yeast. Cohn, for instance, expresses this view in 

 his 'Beitrage zur Biologic der Pflanzen/ 1872, vol. i. heft 2, 

 p. 136. 



Engel adopted Reess's view without criticism ; this 



* Engel, ' Les ferments alcooliques,' Paris, 1872, p. 30. 



