1 66 "DISEASES" OF BEER, 



different species of yeast often bring about different kinds of 

 fermentation ; and he further suggests that it might possibly 

 be of practical importance to carry out the systematic culti- 

 vation of any one species. As is known, it is easier to give 

 expression to an idea than to prove by experiment how far 

 one's views are correct ; but it is only by means of such proof 

 that true success is attained, whether in science or in practice. 

 Bail conducted no experiments, and confined himself to the 

 expression of the above views. He likewise advocated the 

 doctrine, both in the treatise referred to and still more so in 

 his later writings, that Hormiscium cerevisice (beer yeast) and 

 also other yeasts are merely a stage in the development of 

 higher forms e. g. Mucor and other mould fungi. That his 

 researches were quite incorrect, has been proved by the 

 investigations of De Bary and Reess. 



In the zymotechnic journals of the years following, the 

 opinion was expressed here and there that in the fermentation 

 industry, different species or races of both top and bottom 

 yeast occur. Observations in practice would naturally readily 

 lead to such a view, and the researches mentioned above no 

 doubt also helped. 



We have now reached the point where Pasteur took 

 the subject in hand. He published in 1857 a treatise on the 

 lactic acid fermentation, and in this he showed that the fer- 

 mentation was brought about by an organised body which, 

 according to the opinion he then held, was closely related to 

 beer yeast. That he was not at that time able to decide as 

 to what kind of a micro-organism it was, is evident. 



In 1860 Pasteur published the chief results of his numerous 

 and very comprehensive investigations relating to spontaneous 

 generation. He continued this work during the years 

 following, and opposed with great energy and ability the 

 experiments which were made again and again in support of 

 Needham's doctrine of spontaneous generation. Pasteur was 

 able to prove that in such experiments, where the method was 



