FERMENTATION. 535 
from the aperture, and falls like a cataract into troughs 
prepared to receive it. This frothing and foaming of the 
wort is a proof that the fermentation is active. 
Whence comes the yeast which issues so copiously from 
the fermenting tub? What is this yeast, and how did the 
brewer become possessed of it? Examine its quantity 
before and after fermentation. The brewer introduces, 
say 10 cwts. of yeast; he collects 40, or it may be 50 cwts. 
The yeast has, therefore, augmented from four to fivefold 
during the fermentation. Shall we conclude that this 
additional yeast has been spontaneously generated by the 
wort? Are we not rather reminded of that seed which fell 
into good ground, and brought forth fruit, some thirty- 
fold, some sixtyfold, some an hundredfold? On exami- 
nation, this notion of organic growth turns out to be more 
than a mere surmise. In the year 1680, when the micro- 
scope was still in its infancy, Leeuwenhoek turned the 
instrument upon this substance, and found it composed of 
minute globules suspended in a liquid. Thus knowledge 
rested until 1835, when Cagniard de la Tour in France, and 
Schwanu in Germany, independently, but animated by a 
common thought, turned microscopes of improved defini- 
tion and heightened powers upon yeast, and found it bud- 
ding and sprouting before their eyes. The augmentation 
of the yeast alluded to above was thus proved to arise from 
the growth of a minute plant now called Tornla (or 
Saccharomyces) Cerevisice, Spontaneous generation is 
therefore out of the question. The brewer deliberately 
sows the yeast-plant, which grows and multiplies in the 
wort as its proper soil. This discovery marks an epoch in 
the history of fermentation. 
But where did the brewer find his yeast? The reply to 
this question is similar to that which must be given if it 
were asked wliere the brewer found his barley. He has 
received the seeds of both of them from preceding genera- 
tions. Could we connect without solution of continuity 
the present with the past, we should probably be able to 
trace back the yeast employed by my friend Sir Fowell 
Buxton to-day to that employed by some Egyptian brewer 
two thousand years ago. But you may urge that there 
must have been a time when the first yeast-cell was gen- 
erated. Granted exactly as there was a time when the 
first barley-corn was generated. Let not the delusion lay 
