270 FRAGMENTS OF SCIENCE 



quantity before and after fermentation. The brewer in- 

 troduces, say, 10 cwts. of yeast; lie collects 40, or it 

 may be 50, cwts. The yeast has, therefore, augmented 

 from four to five fold 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 sixty-fold, some a hundred- 

 fold? On examination, this notion of organic growth 

 turns out to be more than a mere surmise. In the year 

 1680, when the microscope was still in its infancy, Leeu- 

 wenhoek 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 Grermany, inde- 

 pendently, but animated by a common thought, turned 

 microscopes of improved definition and heightened powers 

 upon yeast, and found it budding 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 Torula (or Saccharomyces) Gere- 

 visioe. 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 where the brewer found his barley. He has 

 received the seeds of both of them from preceding gen- 

 erations. Could we connect without solution of continu- 

 ity the present with the past, we should probably be able 



