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 virulent inoculation had also the advantage of putting a term to the duration 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 Meister 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 comprehend the significance of the experiments which I prosecuted for the purpose of directing attention to the best of the possible interpretations.
Recurring to the methods of progressive attenuation of mortal viruses, and the prophylaxy that may be deduced from it, and the influence 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 rendered 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 constantly identical in itself may lead to a condition proof against rabies by the process of employing very small but daily increasing quantities. This interpretation of the facts of the new method I have studied experimentally. . . .
I need not remark, in conclusion, that the most serious of the questions to be resolved now is perhaps that of the interval that should be observed between the time when the patient is bitten and that at 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.
