STUDIES OX FERMENTATION. 187 



from breweries, where and when it would be hard to say. In 

 the case of the first working brewery, the yeast was, no doubt, 

 derived from some spontaneous fermentation, which took 

 place in an infusion of barley that had been left to itself, or, 

 from some natural spontaneous ferment, and nothing could be 

 easier than to realize this fact again. In the brewing industry 

 there are two distinct modes of fermentation : — " high " fermen- 

 tation and " low " fermentation, some of the distinctive charac- 

 teristics of which we have pointed out in Chapter I. It may 

 be questioned whether the spontaneous yeast employed in the 

 first brewery, or that which a wort left to itself in the present 

 day would yield, would be of the " high " or " low " type. It 

 may be concluded from what we have said on the subject of 

 spontaneous fermentations in wort, that wort, left to itself, 

 would furnish ferments more or less resembling those of wine. 

 We have never obtained in spontaneous fermentations of wort 

 either a distinctly " high " ferment, or a distinctl}^ " low " one, 

 properly so called ; nor, further, have we ever obtained either 

 one of these distinct kinds, with its industrial characteristics, 

 in experiments on the ferments of fruits. What, then, was 

 the origin of the " high " and " low '•* ferments now used by 

 brewers ? What was the nature of their original germs ? 

 These are questions which we are unable to answer, but we are 

 very much inclined to think that we have here another example 

 of the modifications which plants as well as races of animals 

 undergo, and which become hereditary in the course of pro- 

 longed domestication. We know nothing of corn in its wild 

 state, we cannot tell what its first grain was like. We know 

 nothing of the silk-worm in its original state, and we are 

 ignorant of the characters of the race that furnished the first 



These reflections may seem to favour the supposition that 

 there is a real difierence between "high" yeast and "low" 

 yeast, and that both of these differ from spontaneous ferments 

 and the ferments of domestic fruits. These are propositions 

 demanding most careful consideration, for it is generally admitted 



