296 PASTEUR : THE HISTORY OF A MIND 



inserted under the skin of an animal, can give it rabies. 

 But this method of transmission is quite as uncertain and 

 capricious as transmission through the saUva. Rabies 

 does not always appear, and it sometimes does so only after 

 a prolonged incubation of months. Inoculation under 

 the skin, therefore, is an uncertain method. But, said 

 some one in the laboratory of Pasteur, why not try to 

 deposit the virus in the nerve centers, since it is there 

 that it grows and reproduces itself. 



For that purpose it was not necessary to know the 

 microbe, nor even to be sure that there was one; the proof 

 of its presence and its development would not be micro- 

 scopical examination, but the appearance of rabies in 

 the animal inoculated. As a culture medium the nerve 

 tissue offers, moreover, guarantees which one does not 

 find either in the saliva or even in the blood, both of 

 w^hich are much more accessible to contamination from 

 the exterior. Furthermore, it seemed to be a chosen 

 medium for the virus of rabies, and to fulfil naturally 

 for it that condition which was the foundation of the 

 culture method, and which was realized only after much 

 labor in the artificial culture media for the anthrax 

 bacteridium and the microbe of chicken cholera. The 

 main thing was to gain access to it properly and to make 

 an antiseptic inoculation there. The surest way was 

 to attempt to inoculate a dog under the dura mater, 

 by trepanning. "Ordinarily an experiment once con- 

 ceived and talked over was put under way without delay," 

 says Dr. Roux. "This one, on which we were counting 

 so much, was not begun immediately. Pasteur, who 

 had been obliged to sacrifice so many animals in the 

 course of his beneficent studies, felt a veritable repug- 

 nance toward vivisection. He was present without 

 too much squeamishness at simple operations, such as 

 a subcutaneous inoculation, and yet, if the animal cried 



