DISCOVERY OF VACCINES 281 



As all these belonged to the experiments under way, 

 an attempt was made to revive them, and with that 

 end in view, transfers were made from them either into 

 chicken bouillon or into chickens. Many of these made 

 no growth, and also spared and left unimpaired the 

 animals into which they were inoculated, and we were 

 about to throw them away, in order to begin anew, when 

 it occurred to Pasteur to inoculate a fresh young culture 

 into these chickens which, at least in appearance, had 

 so well resisted the inoculations with the cultures 

 made the preceding summer. 



To the surprise of all, perhaps even of Pasteur him- 

 self, who did not expect such a success, almost all of these 

 chickens resisted, whereas new chickens, just brought 

 from the market, succumbed in the ordinary length of 

 time, thus showing that the culture used for the inocu- 

 lation was very active. With one blow, chicken cholera 

 passed to the list of virus diseases and vaccination was 

 discovered! What secret instinct, what spirit of divin- 

 ation impelled Pasteur to knock at this door, which 

 was only waiting to be opened? Here we see clearly 

 the part played by his readings and his former studies, 

 by the incessant ponderings which had been going on 

 in his mind, and by the intervention, in the midst of 

 these obscurities, of this faculty of imagination to which 

 he has referred in the lines that precede, lines written 

 just at the time when he was setting forth, a conqueror, 

 in the realm of his dream. 



He had, in reality, just established between certain 

 microbial diseases and the virus diseases a definite 

 connection which it was to be the task of the future 

 to enlarge and consolidate. There were, then, microbial 

 diseases which did not recur! One could, therefore, 

 prepare vaccines insuring protection against a viru- 

 lent inoculation! Prudently, Pasteur refrained from 



