THE LABORATORY OF THE ECOLE NORMALE. 295 



Impatient with the length of time required for 

 the incubation of the disease, and with the obligation 

 of waiting whole months for the result of an experi- 

 ment, when the subject demanded such numerous 

 ones, Pasteur began to seek some means of producing 

 hydrophobia with certainty and of making it appear 

 more rapidly. Notwithstanding the assertion of a 

 professor of the veterinary school at Lyons that the 

 saliva of the rabid dog alone contained the virus of 

 the disease, and that he had failed in every attempt to 

 inoculate, whether with the substance of the brain or 

 with the spinal marrow of rabid dogs ; Pasteur, with 

 due care as to purity, introduced under the skin of 

 some rabbits and some dogs, divers parts of the brain 

 of a dog which had died in a rabid state. Hydro- 

 phobia declared itself in both dogs and rabbits, with a 

 duration of incubation about equal to that which 

 followed the ordinary bite of a dog. Although it was 

 necessary still to submit to this long uncertainty with 

 regard to the incubation, one great result was obtained : 

 hydrophobia could be inoculated with other matter 

 than saliva. Not only is the saliva always impure, 

 containing a saliva microbe, which is endowed with 

 a special virulence of its own, but it presents other 

 inconveniences. It is necessary, in these researches, 

 to have a supply of material constantly at hand. 

 Now, the saliva loses its rabic virulence in twenty- 

 four hours. The existence of the rabic virulence in 

 15 



