284 INFECTION AND IMMUNITY 



a second communication (December n, 1882) Pasteur 

 reported his success in communicating the disease by 

 intravenous injections of virus obtained from the 

 central nervous system of rabid animals ; also the 

 experimental demonstration of the fact that all forms 

 of rabies may be produced by the same virus ; also, 

 that all parts of the spinal cord of rabid animals are 

 virulent, as well as all parts of the brain ; also that an 

 animal (dog) which had recovered from a mild attack 

 after inoculation proved to be subsequently immune, 

 and that "this observation constitutes a first step 

 toward a discovery of the prophylaxis of rabies." In 

 a subsequent communication (May 19, 1884) Pasteur 

 presented evidence which demonstrated the fact that 

 by successive inoculations in monkeys the period of 

 incubation is prolonged and the virus of the disease 

 attenuated ; that this attenuated (milder) virus from 

 the monkey when inoculated into a dog no longer 

 produces fatal rabies ; and that dogs so treated are 

 subsequently immune. 



Having demonstrated these important facts Pas- 

 teur determined to make a test experiment which 

 should convince the scientific world of the truth and 

 value of his discoveries. At his request a commission 

 was appointed by the Minister of Public Instruction 

 to determine the efficacy of his method as applied 

 to the protection of dogs. In his address before the 



