THE PREVENTION OF HYDROPHOBIA. t^-j-j 



a mad dog, which, as I have just stated, lacks much of being of maxi- 

 mum potency, when transferred to the rabbit, must pass through the 

 systems of several individuals before reaching its maximum. 



A rational application of the results which I have just made known 

 leads readily to the rendering of dogs insusceptible to rabies. We 

 have learned that the experimenter may have at his disposal attenu- 

 ated rabies-viruses of different strengths ; some which are not fatal 

 will protect the system from the effects of more active viruses, and the 

 latter against those which are fatal. Let us take an example. Rabies- 

 virus is obtained from a rabbit which has died from trepanning after 

 a period of incubation which exceeds by several days the shortest 

 time in which the disease may be induced in the rabbit. This invari- 

 ably takes place within seven or eight days after inoculation by tre- 

 panning with the most potent virus. The virus from the rabbit in 

 which the incubation has been long, is inoculated, by trepanning, into 

 a second rabbit, and the virus from this one into a third. With each 

 successive transfer, some of the virus, which becomes stronger and 

 stronger each time, is inoculated into a dog, who becomes gradually 

 more hardened against the operation of the poison, until he is finally 

 found capable of withstanding a fatal virus. He then becomes en- 

 tirely insusceptible to rabies, the virus of a mad dog producing no 

 effect upon him, whether introduced by intra-venous inoculation or by 

 trepanning. By inoculation of the blood of rabid animals, under cer- 

 tain conditions, I have succeeded in greatly simplifying the operations 

 of vaccination, and in producing in the dog the most decided state of 

 insusceptibility. I shall soon make known the details of the experi- 

 ments on this point. 



Until the time when rabies shall have become extinct through vac- 

 cination, the prevention of the development of this affection, in conse- 

 quence of bites by rabid dogs, will be a problem of considerable inter- 

 est. In this direction, the first attempts which I have made give me 

 the greatest hopes of success. The period of incubation after biting 

 is, I have every reason to believe, of such length that the subject may 

 be rendered insusceptible before the fatal form of the disease devel- 

 ops. The preliminary experiments are very favorable to this opinion, 

 but the tests must be infinitely multiplied on various species of ani- 

 mals before therapeutics will have the boldness to try this preventive 

 on man. 



Notwithstanding the confidence with which the numerous experi- 

 ments I have made during the last four years inspire me, I do not 

 announce the facts that point to a possible prevention of hydrophobia 

 without some apprehension. Had I had sufiScient material means, I 

 should have preferred not making this communication till I had so- 

 licited, by the kindness of some of my associates of the Academy of 

 Sciences and the Academy of Medicine, the verification of the conclu- 

 sions I have just made known ; and I have requested M. Failli^res, 



