14 STUDIES ON FERMENTATION. 



and enables us to secure such striking advantages? The expla- 

 nation is simple : the diseased ferments, which we have pointed 

 out, rarely appear at a lower temperature than 10° C. (50° F.), 

 and at that temperature their germs cease to be active. The 

 adoption of low temperatures by brewers is mainly due to this 

 phvsiological fact. On one occasion only have we met with 

 active vibrios (No. 3, Plate I.), at a very low temperature ; these 

 were forming with great difficulty in wort fermenting at 5° C. 

 (41° F.), 



From this we see that the changes which the manufacture of 

 beer has undergone during the present century have been based 

 mainly on the diseases to which beer is liable, either during or 

 after the process of brewing. The fact that English brewers 

 have not as yet adopted "low fermentation^^ may be accounted 

 for, in a great measure, by the difficulty of enlarging existing 

 breweries, in cities like London, to the extent required for the 

 new method of manufacture. Even in the event of public taste 

 demanding a " low beer," English brewers will hesitate a long 

 time before converting their breweries. Such conversion would 

 impose upon them expenses and difficulties of a very serious 

 nature. If ever such a change should take place, it will probably 

 be inaugurated out of London. It is, however, worthy of remark 

 that English brewers, without adopting "low fermentation," 

 have introduced considerable improvements in brewing, especialh^ 

 in the management of the temperature during fermentation ; 

 this must be preserved within narrow and exact limits, for fear 

 of injury to the product. It might easily be shown that these 

 improvements have resulted from the liability of the beer to 

 contract diseases, although this fact may not have been recog- 

 nized by the brewers who have introduced them. 



Besides the yeasts which belong to the two principal kinds 

 of fermentation, there exist many varieties of alcoholic ferment 

 that produce, each of them, a special kind of beer. Among these 

 special beers some are deficient in taste, others in aroma, others 

 in brilliancy. Let us suppose that in the manufacture of a 

 beer with one of these yeasts, from which a peculiar flavour 



