Ill PASTEUE AND HYDROPHOBIA 169 



chemical substances produced by the microbe. In 

 the spinal cord of a rabic animal removed and hung- 

 up in a glass jar to dry, the vaccin substance appears 

 to remain intact, whilst the toxin diminishes, and 

 finally is all destroyed. 



As stated in the essay to which this note is an 

 appendix, M. Pasteur does not use in his treatment 

 of persons bitten by rabid animals an attenuated virus, 

 that is, a virus containing a weakened toxin, but, on 

 the contrary, a virus of increased strength. The rabic 

 virus as found in the doe: is of medium stren2:th and 

 rapidity of action ; by cultivation from monkey to 

 monkey it can be attenuated, rendered slower and less 

 deadly in its action. But by cultivation from rabbit 

 to rabbit M. Pasteur obtains a virus of maximum 

 intensity, Avhich kills in seven days, and it is this 

 which he makes use of in treating persons who have 

 been already infected by the virus of medium strength 

 from the tooth of a dog. The explanation of this is, 

 of course, related to the fact that M. Pasteur has not 

 in his treatment to prepare his patients to withstand 

 a future inoculation by dog- bite, but has to treat 

 persons already bitten, already harbouring in their 

 bodies the slowly- acting form of the virus derived 

 from the doo^. 



"It is," Dr. Bouchard observes, "necessary to 

 overtake this latter virus, to act more quickly than it 

 does, in fact to make use of a vaccinating virus of 

 briefer incubation, to employ in consequence an in- 

 tensified virus. Inoculated beneath the skin, a rabic 

 virus of any kind will often give vaccinal protection ; 



