A HISTORY OF SCIENCE 



of every imaginative physician, of every working micro- 

 biologist. 



As it happened, the world was not kept long in sus- 

 pense. Almost before the proposition had taken 

 shape in the minds of the other leaders, Pasteur had 

 found a solution. Guided by the empirical success of 

 Jenner, he, like many others, had long practised inocu- 

 lation experiments, and on February 9, 1880, he an- 

 nounced to the French Academy of Sciences that he had 

 found a method of so reducing the virulence of a dis- 

 ease germ that when introduced into the system of a 

 susceptible animal it produced only a mild form of 

 the disease, which, however, sufficed to protect against 

 the usual virulent form exactly as vaccinia protects 

 against small - pox. The particular disease experi- 

 mented with was that infectious malady of poultry 

 known familiarly as "chicken cholera." In October 

 of the same year Pasteur announced the method by 

 which this " attenuation of the virus," as he termed it, 

 had been brought about by cultivation of the dis- 

 ease germs in artificial media, exposed to the air, and 

 he did not hesitate to assert his belief that the method 

 would prove "susceptible of generalization" that is 

 to say, of application to other diseases than the par- 

 ticular one in question. 



Within a few months he made good this prophecy, 

 for in February, 1881, he announced to the Academy 

 that with the aid, as before, of his associates MM. Cham- 

 berland and Roux, he had produced an attenuated 

 virus of the anthrax microbe by the use of which, as he 

 affirmed with great confidence, he could protect sheep, 

 and presumably cattle, against that fatal malady. 



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