312 THE LIFE OF PASTEUR 



only produce bacteridia likewise weakened in their swarming 

 faculties." 



Thus is obtained and enclosed in inalterable spores a vaccine 

 ready to be sent to every part of the world to preserve animals 

 by vaccination against splenic fever. 



On the day when he became sure of this discovery, Pasteur, 

 returning to his rooms from his laboratory, said to his family, 

 with a deep emotion " Nothing would have consoled me if this 

 discovery, which my collaborators and I have made, had not 

 been a French discovery." 



He desired to wait a little longer before proclaiming it. Yet 

 the cause of the evil was revealed, the mode of propagation 

 indicated, prophylaxis made easy; surely, enough had been 

 achieved to move attentive minds to enthusiasm and to deserve 

 the gratitude of sheep owners ! 



So thought the Society of French Agricultors, when it 

 decided, on February 21, 1881, to offer to Pasteur a medal of 

 honour. J. B. Dumas, detained at the Academic des Sciences, 

 was unable to attend the meeting. He wrote to Bouley, who 

 had been requested to enumerate Pasteur's principal discoveries 

 at that large meeting " I had desired to make public by my 

 presence my heartfelt concurrence in your admiration for him 

 who will never be honoured to the full measure of his merits, of 

 his services and of his passionate devotion to truth and to our 

 country." 



On the following Monday, Bouley said to Dumas, as they 

 were walking to the Academic des Sciences, "Your letter 

 assures me of a small share of immortality." 



" See," answered Dumas, pointing to Pasteur, who was pre- 

 ceding them, "there is he who will lead us both to 

 immortality." 



On that Monday, February 28, Pasteur made his celebrated 

 communication on the vaccine of splenic fever and the whole 

 graduated scale of virulence. The secret of those returns to 

 virulence lay entirely in some successive cultures through the 

 body of certain animals. If a weakened bacteridium was 

 inoculated into a guinea-pig a few days old it was harmless ; 

 but it killed a new-born guinea-pig. 



"If we then go from one new-born guinea-pig to another," 

 said Pasteur, " by inoculation of the blood of the first to the 

 second, from the second to a third, and so on, the virulence of 

 the bacteridium that is : its adaptability to development 



