THE CONQUEST OF HYDROPHOBIA 207 



ous tissue proved fruitless. How then could one 

 apply the principle of attenuation in this disease 

 and obtain a vaccine as in chicken cholera and 

 anthrax? Pasteur attacked the problem by at- 

 tempting to weaken the virus in its favorite seat, 

 the nervous system. The spinal cord of a rabbit 

 with hydrophobia was removed and suspended in 

 a sterile tube. Into this the air was admitted 

 through a plug of cotton wool, and was kept dry 

 by a piece of caustic potash in the bottom of the 

 tube which absorbed the moisture. After fourteen 

 days an emulsion of the cord injected into a dog's 

 brain showed that the material had lost its power 

 of producing rabies. Then an injection from a 

 cord dried for thirteen days was tried, followed by 

 an injection from a cord dried only twelve days, 

 and so on until finally material was used from a 

 rabbit that had died on the same day. Several 

 dogs that had been put through this treatment were 

 allowed to be bitten by rabid animals. The brains 

 of other protected dogs were inoculated directly. 

 All of the protected animals failed to develop 

 hydrophobia. 



The success of these experiments was very en- 

 couraging. Realizing that his conclusions would 

 probably be attacked, Pasteur desired that his dis- 



