26 LOUIS PASTEUR. 



industries. The large brewery of to-day is impossible without the 

 microscope, and to the stimulus given by these discoveries of 

 Pasteur has been due the great centralisation of brewing. 



The next problem that attracted the attention of Pasteur was 

 the dreaded anthrax. For several years this devastating disease 

 had been the subject of scientific investigation. Already its con- 

 nection with micro-organisms had been made probable, and indeed 

 had been demonstrated. Many problems had been solved, but 

 many still remain to be solved in connection with this pestilence 

 of the agriculturist. As usual, Pasteur began at the beginning, 

 taking nothing for granted, even of the facts that had been essen- 

 tially demonstrated. His experiments resulted in a more complete 

 demonstration of the relation between the anthrax bacillus and the 

 disease, showed the method of action of the germ, demonstrated 

 the source from which it was frequently derived by cattle, differ- 

 entiated between this disease and one or two others closely 

 resembling it among animals, disproved all of the objections that 

 had been raised by those who disbelieved in the casual nature 

 of the bacilli, and, in short, brought this subject upon the same 

 sure foundation as that of pebrine which he had so triumphantly 

 solved ten years before. Nor was this all. The greatest dis- 

 covery of his life was to follow. To Pasteur's pecuhar trait of 

 mind it was not enough to discover the cause without searching 

 for the remedy. It was the practical question which appealed to 

 him. Pasteur recognised the fact that in the human race one 

 attack of an infectious disease frequently renders an individual 

 immune against a second attack. He also remembered that pro- 

 tection against small pox had been known to be produced by 

 vaccination. 



Acting upon these suggestions the questions arose in his mind 

 whether it was not possible to give to domestic animals, subject to 

 this devastating disease, a milder type of the disease in question, 

 from which they should readily recover, but which would give 

 them immunity against a second attack. The principle was a new 

 one, and outlined a new, bold plunge into the mysteries of nature. 

 It was not, however, in the investigations of anthrax that the 

 remedy first suggested itself, but rather in a side investigation upon 

 the subject of another germ disease known as fowl cholera. Every 



