250 SCIENCE PROGRESS. 



certainly manifested itself in the inoculated animal, and 

 at an earlier period than when the inoculation was made 

 under the skin. Applying what had been found to occur 

 in swine fever, Pasteur found that canine virus is more 

 powerful than virus that has been passed through a long 

 series of monkeys, whilst that passed through rabbits 

 gradually acquires such activity that the period of incuba- 

 tion of the disease, — i.e., the time which the disease takes to 

 manifest itself after inoculation — is reduced to one half. 

 Here then it was possible to obtain materials for inoculation 

 of all degrees of virulence. Was it not possible by a pro- 

 cess of gradual acclimatisation of the tissues to the presence 

 of the virus to render a patient immune to the action of 

 the most powerful virus ? This was proved, in the first 

 instance, by the use of monkey virus, and then, virus 

 from dogs and rabbits, but all the more recent experiments 

 have been carried on with material derived from the spinal 

 cord of the rabbit. Having observed that the cords of 

 rabbits that had been dead for some time contained a less 

 virulent poison than the cords of freshly killed animals 

 — this being especially the case in dry weather — he 

 came to the conclusion that he might obtain vaccines 

 of all degrees of virulence by simply exposing the cords of 

 rabbits that had succumbed to hydrophobia to dry air for 

 different periods. The fresh cord would give the strongest 

 virus, that exposed longest (fifteen days) the weakest. 

 This was found to be the case, and dogs were protected 

 and cured even when the treatment was commenced only 

 after the animal had been bitten by a rabid animal. 



The application of this method to the human subject was 

 first made in the case of a little lad, Joseph Meister, aged 

 nine years, who had been badly bitten by a dog. As the 

 dog was undoubtedly mad, and as there was little chance of 

 the survival of the child in the ordinary course of events. 

 Pasteur resolved after consulting with Professors Vulpian 

 and Grancher, who agreed to share the responsibility, to 

 treat the boy as he had treated the dogs that he had already 

 been successful in protecting. The boy recovered, and 

 since that time there can be no doubt that, although there 



