186 X LOUIS PASTEUR. 



without doubt produces in the constitution of this liquid, 

 after the manner of ferments, modifications which 

 speedily destroy the infected animal.' ' For a long 

 time,' he repeated, ' physicians and naturalists have 

 admitted theoretically that contagious diseases, serious 

 epidemic fevers, the plague, &c., are caused by invisible 

 animalculae, or by ferments, but I do not know that 

 these views have ever been confirmed by any positive 

 observations.' 



A few months after the publication of the results 

 obtained by Davaine, two professors of Yal-de-Grace, 

 MM. Jaillard and Leplat, sought to refute the pre- 

 ceding conclusions. After having inoculated rab- 

 bits and dogs with various putrefying liquids filled 

 with vibrios, they could not cause the death of these 

 animals. To bring about this result it was necessary 

 to introduce into the blood of these dogs and rabbits 

 several cubic centimeters of very putrid liquid. Again 

 in this case, which only added another example to the 

 experiments of Gaspard and Magendie upon the action 

 of putrid liquids, they failed to generate any virulence 

 in the blood. Davaine had no difficulty in showing 

 that MM. Jaillard and Leplat's experiments were made 

 under conditions totally different from his ; that lie, 

 Davaine, had not made use of the vibrios or bacteria 

 of unselected infusions, but of bacteria which had 

 br<-n found in the blood of sheep which had died 

 from sang-de-ratc. 



