FEEMENTATION. 271 



the knowledge which reveals to us the nature, and 

 which assures the extirpation, of a disorder so virulent 

 and so vile, worth the price paid for it ? It is exceed- 

 ingly important that assemblies like tlie present should 

 see clearly the issues at stake in such questions as this, 

 and that the properly informed sense of the community 

 should temper, if not restrain, the rashness of those 

 who, meaning to be tender, become agents of cruelty 

 by the imposition of short-sighted restrictions upon 

 physiological investigations. It is a modern instance 

 of zeal for Grod, but not according to knowledge, the 

 excesses of which must be corrected by an instructed 

 public opinion. 



And now let us cast a backward glance on the field 

 we have traversed, and try to extract from our labours 

 such further profit as they can yield. For more than 

 two thousand years the attraction of light bodies by 

 amber was the sum of human knowledge regarding 

 electricity, and for more than two thousand years fer- 

 mentation was effected without any knowledge of its 

 cause. In science one discovery grows out of another, 

 and cannot appear without its proper antecedent. Thus, 

 before fermentation could be understood, the micro- 

 scope had to be invented, and brought to a considerable 

 degree of perfection. Note the growth of knowledge. 

 Leeuwenhoek, in 1680, found yeast to be a mass of 

 floating globules, but he had no notion that the globules 

 were alive. This was proved in 1835 by Cagniard de la 

 Tour and Schwann. Then came the question as to the 

 origin of such microscopic organisms, and in this con- 

 nexion the memoir of Pasteur, published in the 

 ' Annales de Chimie ' for 1862, is the inauguration of a 

 new epoch. 



On that investigation all Pasteur's subsequent 

 13 



