INOCULATION AGAINST HYDROPHOBIA. 293 



Joseph Meister, then, has escaped, not only the rabies which his 

 bites would have developed, but also that with which I inoculated him 

 in order to confirm the immunity secured by the treatment — a more 

 virulent rabies than that of the mad dog. The final extremely viru- 

 lent inoculation had also the advantage of putting a term to the dura- 

 tion of the apprehensions we might entertain as to the consequences 

 of the bites. If rabies was to break out, it would declare itself more 

 speedily with a more virulent virus than that of the bites. From the 

 middle of August I regarded the future of the health of Joseph Meis- 

 ter with confidence ; and now, after three months and three weeks 

 have passed since the accident, his health leaves nothing to be 

 desired. 



What interpretation shall we give to the new method which I 

 have just described for preventing rabies after being bitten ? I do 

 not intend to consider this question in full to-day ; but will limit 

 myself to a few preliminary details, such as may help to compre- 

 hend the significance of the experiments which I prosecuted for the 

 purpose of directing attention to the best of the possible interpre- 

 tations. 



Recurring to the methods of progressive attenuation of mortal 

 viruses, and the prophylaxy that may be deduced from it, and the in- 

 fluence of the air in the attenuation being given on the other side, the 

 first thought that occurs in trying to account for the effects is that the 

 continued presence of rabies-infected marrows in contact with dry air 

 progressively diminishes the intensity of their virulence till it is ren- 

 dered nil. We are, therefore, led to believe that the prophylactic 

 method under consideration rests upon the employment at first of virus 

 without appreciable activity ; then of weak viruses, and then of those 

 of greater and greater virulence. I shall show, further on, that the 

 facts are in disaccord with this view. I shall prove that the increase 

 in the length of the periods of incubation of the rabies, communicated 

 day after day to rabbits, as I have just said, to test the condition of 

 virulence of our marrows, dried in contact with the air, is an effect of 

 impoverishment in the quantity of the virus contained in the marrows, 

 and not an effect of its impoverishment in virulence. 



We may suppose that inoculation with a virus of virulence con- 

 stantly identical in itself may lead to a condition proof against rabies 

 by the process of employing very small but daily increasing quanti- 

 ties. This interpretation of the facts of the new method I have stud- 

 ied experimentally. . . . 



I need not remark, in conclusion, that the most serious of the ques- 

 tions to be resolved now is perhaps that of the interval that should be 

 observed between the time when the patient is bitten and that s.t 

 which the treatment should be begun. In the case of Joseph Meister, 

 the interval was two days and a half. But there is reason to suppose 

 that it may sometimes be much longer. 



