78 PASTEUR AND AFTER PASTEUR 



always have a latent period of six to seven days ; 

 and it would always cause death.* 



Then came the first step toward a protective 

 treatment. As he had attenuated the virus of 

 fowl-cholera, by mere keeping, so he now attenuated 

 the virus of rabies, by mere keeping. If the spinal 

 cord of a rabbit, which had died of an inoculation 

 of virus ficce, were removed of course by a strictly 

 aseptic method and kept in an aseptic flask, in 

 dried and filtered air, in the dark, at a constant 

 temperature, it would steadily lose virulence, day 

 by day. At the end of fourteen days, it would be 

 wholly non- virulent. Thus, by inoculating a suffi- 

 cient number of rabbits, he was able to prepare and 

 stock, in a complete set of cords, the dried virus of 

 rabies, in every shade of strength, from non- virulence 

 up to fullest virulence. With measured doses of 

 these cords, rubbed up in a little water, and injected 

 under the skin, he could immunise dogs ; beginning 

 with a dose of fourteen-days' cord, then a dose of 

 thirteen-days' cord, and so on, up to a dose of cord 

 at full virulence. These dogs, thus immunised, were 

 submitted to the bite of mad dogs, or even to sub- 

 dural inoculation ; and took no harm. 



That is the story, in four pages, of near four 

 years of work. In May, 1884, he asked the French 



* It is satisfactory to know that rabbits affected with 

 rabies do not suffer in the same way as dogs and some other 

 animals, but become subject to a painless kind of paralysis. 



