BIOLOGICAL THERAPEUTICS 



547 



Prevention by Pasteur Method. 



In the Pasteur method^ rabies vaccine is prepared by inoculating 

 rabbits subdurally with fixed virus which in six to eight days produces 

 paralysis. When completely paralyzed, the rabbits are killed and the 

 spinal cords are removed under aseptic conditions. Fixed virus is rabies 

 virus which, by continuous passage through rabbits, has reached a stage 

 of maximum virulence for that animal. Rabbits of four or five pounds 

 weight, inoculated subdurally with fixed virus, will die in eight days. By 

 the passage of the virus through rabbits, the virulence is enhanced for 

 the rabbit but attenuated for other animals and man. Besides being 

 weakened by the passage through rabbits, the virus is further attenuated 

 by drying the spinal cords for varying periods of time. The cords are 

 suspended over a layer of potassium hydroxide and kept at a temperature 

 of 22° C. from one to eight days. As a result of this drying process, the 

 virus in the substance of the cords is gradually weakened or attenuated. 

 If suspended in this manner long enough, the virus may be entirely de- 

 stroyed: the virus being strongest when the cords are fresh. Each day 

 during the process of drying, the strength decreases in direct proportion 

 to the extent of 

 the drying. In 

 the preparation 

 of each dose of 

 rabies vaccine, 

 a portion of a 

 rabbit's cord, in 

 which the virus 

 has been prop- 

 ly a 1 1 enuated 

 by drying for 

 periods of one 

 to eight days, is 

 e m u 1 sified by 

 grinding under 

 a s e ptic condi- 

 tions with glyc- 

 erin, and filled 

 into vials. Pas- 

 teur's antirabic treatment consists of the injection of 25 doses of rabies 

 vaccine, the injections being given daily for 21 successive days. 



The vaccination of human beings against rabies by the Pasteur 

 method has been well established in every country of the world. Rabies 

 vaccine has been used to only a limited extent in veterinary practice. 

 The apparent neglect of utilizing this treatment for animals is due to the 

 fact that vaccination by the Pasteur method, aside from the considerable 

 expense of the vaccine, requires 25 injections in order to produce the 

 desired immunity which, of course, necessitates a large number of visits 

 by the veterinarian. Whereas, with the dilution method, immunity is 

 established with six injections, which in itself gives decided advantage 

 to this form of vaccination and it is therefore given preference for the 

 protective treatment oiQimtmsl. by Microsoft® 



Negri Bodies in a Ganglion Cell; (a) Nucleus of Ganglion 



Cell; (b) Covering of Negri Body; (o) Large 



and Small Internal Bodies 



