STUDIES ON RABIES 295 



method of transmission was most micertain. The 

 incubation period for rabies is extremely variable; 

 it may be some days or it may be several months. 

 Nothing is more unendurable for an experimenter than 

 these long and uncertain delays between an experi- 

 ment and its results. Moreover, sometimes it happens 

 that the bitten or inoculated animal does not die, and 

 everything has to be done over again. Finally, as a 

 last obstacle, numerous attempts carried on for a long 

 time in the laboratory of Pasteur, and elsewhere, had 

 shown that it was impossible to discover in the saliva 

 of rabid animals any organism having an assured etio- 

 logical relation to the disease. Pasteur, after having 

 believed that he had discovered it, had renounced this 

 idea, which he had had the prudence not to pubhsh, 

 so that he attacked the question without knowing 

 whether the disease was a virus disease, without knowing 

 or being able to cultivate the microbe, and even without 

 having a certain and quick method of inoculation. It 

 is here that we shall soon see the power of the experi- 

 mental method when it is handled at the same time 

 with prudence and audacity. It is a marvelous tool, 

 having an extraordinary power of penetration, being 

 able, provided it is handled by one who thoroughly 

 understands it, to work even in obscurity, like those 

 drills which attack and pulverize everything that is 

 presented to them in the depths of a black pit, provided 

 that they are entirely in the grasp of the man who di- 

 rects them. 



The general symptoms of rabies bore witness that it was 

 especially the nerve centers which were attacked. Dr. 

 Duboue, of Pau, had already observed this and concluded 

 that not simply the saliva of a mad animal but also its 

 nerve-substance should be virulent. Experiment has 

 demonstrated the justice of this conclusion. Nerve tissue, 



