190 LOUIS PASTEUR, 



guishable from the true torula or yeast-plant. Many 

 mysteries of our breweries were cleared up by this in- 

 quiry. Without knowing the cause, the brewer not 

 unfrequently incurred heavy losses through the use of 

 bad yeast. Five minutes' examination with the micro- 

 scope would have revealed to him the cause of the 

 badness, and prevented him from using the yeast. He 

 would have seen the true torula overpowered by foreign 

 intruders. The microscope is, I believe, now everywhere 

 in use. At Burton-on-Trent its aid was very soon in- 

 voked. At the conclusion of his studies on beer M. 

 Pasteur came to London, where I had the pleasure of 

 conversing with him. Crippled by paralysis, bowed 

 down by the sufferings of France, and anxious about his 

 family at a troubled and an uncertain time, he appeared 

 low in health and depressed in spirits. His robust 

 appearance when he visited London, on the occasion of 

 the Edinburgh Anniversary, was in marked and pleasing 

 contrast with my memory of his aspect at the time to 

 which I have referred. 



While these researches were going on, the Germ 

 Theory of infectious disease was noised abroad. The 

 researches of Pasteur were frequently referred to as 

 bearing upon the subject, though Pasteur himself kept 

 clear for a long time of this special field of inquiry. 

 He was not a physician, and he did not feel called upon 

 to trench upon the physician's domain. And now I 

 would beg of him to correct me if, at this point of the 

 Introduction, I should be betrayed into any statement 

 that is not strictly correct. 



In 1876 the eminent microscopist, Professor Cohn, 

 of Breslau, was in London, and he then handed me 

 a number of his ' Beitrage,' containing a memoir 

 by Dr. Koch on Splenic Fever (Milzbrand, Charbon, 



