FERMBNTA TION. 535 



from the aperture, and falls like :i cataract into troughs 

 red to receive it. This frothing and foaming of the 

 w>rt is a proof that the fermentation is act i 



Whence conies the yeast which issues so copiously from 

 the fermenting tub!' "What is this yeast, ami how (lid the 

 bn-wer 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 he 50 cwts. 

 Tlie yeast has, therefore, augmented from four to fivefold 

 during the fermentation. Shall we conclude that this 

 additional yeast has been spontaneously generated by the 

 P Are we not rather reminded of that seed \\ hich fell 

 into good ground, and brought forth fruit, some thirty- 

 fold, some eixtyfold, 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 

 Schwann in Germany, independently, but animated ly a 

 common thought, turned microscopes of improved deiini- 

 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 Tnrula (or 

 SaccMromyces) Cerevisice. Spontaneous generation is 

 therefore out of the question. The brewer deliberately 

 sows the yeast-plant, which grows and multiplies in the 

 wort us its proper soil. This discovery marks an epoch in 

 the history of fermentation. 



Hut where did the brewer find his yeast? The reply to 

 this question is similar to that which must be given if it 

 were asked where the brewer found his barley. He has 

 red the seeds of both of them from preceding genera- 

 Could we connect without solution of continuity 

 the present with the past, wo should probably be able to 

 back the yeast employed by my friend Sir Powell 

 .11 to-day to that employed by -yplian b. 



two thousand years sigo. : may urge that there 



have been a time when the first yeast-crll 

 crated. (Iran 1 ..-tly as ilu-iv when I he 



Brat bariey-oorn WM generated, Let not the delusion lay 



