48 



for the application of the principle of action to 

 which it leads, there is this advantage on the side 

 of hydrophobia, that from the prolonged period 

 usually taken for incubation after the introduction 

 of the poison in the ordinary way, time is given 

 for the artificial inoculations by subcutaneous 

 injection to produce their efiect and to render 

 the system refractory to the further development 

 of disease. I have been an eye-witness of Pasteur's 

 work. It is from the nerve centre, the seat from 

 which the symptoms of the disease start, that he 

 obtains his virus. Employed for inoculation in a 

 fresh state it produces a fatal disease, and the dis- 

 ease has been transmitted successively on through 

 a number of animals with the result that the last 

 affected animal yields as strong a virus as the first. 

 Kept in a pure dry air, attenuation advances, 

 and after a certain time the nerve centre loses its 

 disease-producing power. Used for inoculation at 

 a given period of preservation it produces an 

 effect which renders an animal resistant to the 

 influence of inoculation with the virus in a fresh 

 state, and Pasteur contends that it acts similarly 



