THE PROBLEM OF IMMUNITY 299 



the aid of MM. Vulpian and Grancher, the experi- 

 ments were extended to man. To-day almost 20,000 

 persons have undergone this antirabic treatment and the 

 mortality occurring among these treated persons has 

 been less than 5 per thousand. 



"The discovery of the prophylaxis for rabies aroused 

 everywhere great enthusiasm. It increased the popu- 

 larity of Pasteur more than all his former works. In 

 return for such a benefaction, the great public desired 

 to manifest its gratitude in a manner worthy of itself 

 and of the man it wished to honor. It was then that 

 the subscription was started which has made possible 

 the founding of the Pasteur Institute." 1 



Once again the method had brought forth fruit. We 

 could further cite, as proof of its value, the vaccination 

 for erysipelas of swine, preeminent among the workers 

 on which was the regretted Thuillier. But we should 

 find therein only what we already know. We are not 

 writing the history of the work of Pasteur, but that of 

 his mind, and it is better to take up an aspect of the 

 question of viruses which we have not yet considered. 



VI 

 THE PROBLEM OF IMMUNITY 



The theoretical importance of all these facts was 

 superior even to their practical importance. This 

 method of the physiological study of microbes in pure 

 cultures which had at first given the etiology of the 

 different diseases studied, which later had furnished 

 all the ideas which we have just summed up on varia- 

 tions in virulence, was about to exhibit a new fecundity 

 by opening up the problem of immunity, on which 



1 Roux, 1. c., p. 543. 



