170 The Story of the Bacteria 



Pasteur, is treated by drying the nerve tissue 

 in the air, in which process its virulence 

 steadily diminishes. Thus it is possible to 

 get 'material of all grades of strength. So 

 that if a person bitten by a mad dog be injected 

 at first with a long-dried material, then day 

 after day with that which has been dried for 

 a shorter time, at length with no symptoms 

 whatsoever to indicate that his cells have 

 been responding to a powerful infective agent, 

 he has acquired complete immunity or pro- 

 tection from the disease, which has not been 

 permitted to develop. 



The mortality from hydrophobia before the 

 day of preventive inoculation was about six- 

 teen per cent. Through this treatment it has 

 been reduced to about two tenths of one per 

 cent. 



In the early days of our knowledge of 

 bacteria, the highest hope was cherished that 

 it would soon be possible to destroy bacteria 

 in the body by disinfectants. But this hope 

 soon faded, for it was found that any such sub- 

 stance strong enough to be effective would kill 

 the body cells as soon as it would the bacteria. 



