VACCINE OR OPSONIC THERAPY 113 



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tions of small quantities of virus whose virulence has 

 been attenuated by unfavorable environment, the un- 

 favorable environment in small-pox being the cow; in 

 rabies, the drying under unfavorable atmospheric con- 

 ditions. 



Effects. It is not possible to obtain an exact estimate 

 of the mortality of hydrophobia before the advent of the 

 vaccination treatment, but it is placed not lower than 

 10 per cent. Under the vaccine treatment it has been 

 lowered to much less than i per cent. Its value is, 

 therefore, unquestioned. 



Cholera Vaccine (Haffkine's Cholera Vaccine). 

 Like small-pox and rabies vaccination, cholera vaccina- 

 tion consists in the inoculation with attenuated cultures 

 of the germ of cholera. Unlike them, however, the 

 germ of the disease has been identified and grown arti- 

 ficially for the production of the vaccine. Two vaccines 

 are used, a weaker and a stronger one. Injections of 

 the virulent germs causes excessive tissue destruction at 

 the site of injection unless the individual has been 

 partially immunized by the injection of the weaker vac- 

 cine. The attenuated culture is produced by growing 

 the cholera bacteria upon agar at a temperature of 39 C. 

 in a current of air. The stronger one (and here the 

 method differs radically from all other methods of 

 immunization) is produced by growing the germs on 

 living guinea-pigs. The germs from the peritoneal 

 exudate of the first pig inoculated are incubated for ten 



