74 PASTEUR AND AFTER PASTEUR 



through and through, by a leisurely, accurately 

 measured, standardised course of progressive doses : 

 and the latent virus would thus have lost its one 

 and only opportunity of killing him. 



The working out of this theory, from 1881 to 

 1885, was beset with all kinds of difficulties. To 

 guide him, he had the conviction that rabies does 

 not " come of itself" : that dogs cannot " go mad " : 

 that rabies must be begotten of rabies.! But this 

 fact, which now we all accept, was held open to 

 doubt, thirty or more years ago. Again, he was 

 unable to discover the germs of the disease : he 

 had therefore to alter his methods of research. It 

 goes without saying, that the work was not only 

 difficult but dangerous : he did not mind that : but 

 he did mind, heavily, the final step, from the 

 immunising of animals to the immunising of man. 

 He was sixty-three, when he took that step : and 

 it is certain that the frightful strain of 1885 aged 

 him. Happily for mankind, his work, by 1885, 

 was everlasting : he had founded and established 

 a new kingdom of science : he had taught the 

 whole world a new way of thinking of the in- 

 fective diseases, and a new way of dealing with 

 them. 



His experimental study of rabies began, of 

 course, with inoculations of saliva. So early as 



