VACCINE-THERAPY 137 



the history and symptoms are obscure, and further inquiry 

 is essential in order to arrive at a positive conclusion. 



On microscopical examination of sections of the medulla 

 and cerebellum of a rabid animal, Negre found certain 

 bodies. These bodies stain pink with Van Grieson's stain, 

 the nerve cells are blue, and the red corpuscles colourless 

 or faintly yellow. 



Further, if medullary extract of an animal suspected of 

 dying from rabies is injected into another animal, and that 

 animal develops symptoms of rabies, the results are con- 

 clusive. 



Pasteur was the first to demonstrate the fact that a 

 recovered animal could not be artificially affected later 

 with even large doses of the active virus, and on this basis 

 he introduced an antirabic vaccine. He took a rabbit 

 and infected it by giving a subdural injection with fixed 

 virus, after which he carefully dissected out under proper 

 precautions the medulla and spinal cord and suspended it 

 in a long tube at the bottom of which was placed pieces of 

 caustic potash, and subjected the whole to a constant 

 temperature of 23° C. By this process it was found the 

 cord became dry and also lost a large proportion of its 

 virulence. Thus it was ascertained if a cord dried for five 

 days in this manner would, if introduced into an animal, 

 produce rabies on the eighth ; if dried for nine days the 

 disease would make itself manifest on the fifteenth day ; 

 and if dried for fourteen days the effects of the virus would 

 be nil. 



Therefore a medulla and cord subjected to heat for 

 fourteen days would give daily for the same number of 

 days fourteen doses each, varying in virulence. 



Pasteur injected into dogs the most attenuated dose first, 

 and by diminishing the attenuation he found the time 

 came when a complete degree of immunity was arrived at. 

 So much so, that a dog so treated, if bitten by a rabid dog, 

 was proof against infection. Moreover, he also proved if 

 up to a given time after an animal had been bitten the 



