RABIES 77 



with a trephine ; the dose of medulla, rubbed up in 

 a few drops of sterilised fluid, was put under the 

 dura mater through a hollow needle ; and the 

 wound was closed. This subdural method was 

 infallible : it gave a positive result in every case, 

 and a more rapid development of the disease. 

 The latent period, with this method, was never 

 more than twenty days. 



But it was not enough, that he should shorten 

 the latent period : he must fix it, he must get it 

 down to a standard number of days, and maintain 

 it there. He could do nothing, till he had done 

 that. He must have his virus fixe: he must be 

 able to determine the very day on which the disease 

 should flare up. And this he did. As he had 

 intensified the virus of anthrax, by passing it 

 through a series of new-born guinea-pigs, so he 

 now intensified the virus of rabies, by passing it 

 through a series of rabbits : the latent period, as 

 the series of inoculations went on, became shorter 

 and shorter. Finally, it came down to seven days, 

 or a few hours less. There, it stopped : it could 

 not be shortened below six to seven days. The 

 virus now had attained its fullest strength, and 

 was even stronger than the virus of an ordinary 

 case of the disease. Moreover, it retained its 

 strength, unimpaired, through any number of sub- 

 sequent passages from animal to animal. It would 



