FERMENTATION. 287 



Pasteur followed this parasitic destroyer from year to 

 year, and led by his singular power of combining facts 

 with the logic of facts, discovered eventually the 

 precise phase in the ' development of the insect when 

 the disease which assailed it could with certainty be 

 stamped out. Pasteur's devotion to this enquiry cost 

 him dear. He restored to France her silk husbandry, 

 rescued thousands of her population from ruin, set the 

 looms of Italy also to work, but emerged from his 

 labours with one of his sides permanently paralysed. 

 His last investigation is embodied in a work entitled 

 * Studies on Beer/ in which he describes a method 

 of rendering beer permanently unchangeable. That 

 method is nut so simple as those found effectual with 

 wine and vinegar, but the principles which it involves 

 are sure to receive extensive application at some future 

 day. 



There are other reflections connected with this sub- 

 ject which, even were they now passed over without re~ 

 mark, would sooner or later occur to every thoughtful 

 mind in this assembly. I have spoken of the floating 

 dust of the air, of the means of rendering it visible, and 

 of the perfect immunity from putrefaction which accom- 

 panies the contact of germless infusions and moteless air. 

 Consider the woes which these wafted particles, during 

 historic and pre-historic ages, have inflicted on man- 

 kind ; consider the loss of life in hospitals from putre- 

 fying wounds ; consider the loss in places where there 

 are plenty of wounds, but no hospitals, and in the ages 

 before hospitals were anywhere founded; consider the 

 slaughter which has hitherto followed that of the battle- 

 field, when those bacterial destroyers are let loose, often 

 producing a mortality far greater than that of the 

 battle itself; add to this the other conception that in 

 times of epidemic disease the self-same floating matter 



