274 LOCAL ILSSUE REACTIVITY 



tion alter eight days. Higher dilutions ol horse serum also elicited 

 it but only u])on repeated seirsiti/in^ injections and alter longer 

 incubation j)eriocls, /.r., dilut ion 1:100, lourteen days. V\\v human 



^ 



X 



-^ "'''BWi'("«^i«»»». 



Fk;. 31. Ral)bit sensitized b) single injection of horse serum six clays previously, 

 iecci\ed intradermal injection ol 0.25 c.c. of undilutef/ B. typhosus active principles. 

 Twenty-foin hoins later rabbit was injected intravenously with horse seriun. Appear- 

 ance of reaction at prej^ared skin site ninety-six hours after intra\enous injection of 

 horse scrnni. 



sertuii appeared to be of high antigenicity iov raljbits because 

 even 1 c.c. of dilution 1:10,000 injected twice induced sensitiza- 

 tion eight days after the second sensitizing injection. The antigen 

 ior test injections could also be used in comparatively smaller 

 amounts, i.e., 1 c.c. horse serimi diluted 1:100. The sensitization 

 was also successfully induced through the intracranial routes 

 ^vithin fhe to nine days. 



There was an uiujuestionable specificity of the sensitization 

 described. Rabbits sensitized to small amounts of horse serum, 

 while showinti reactions with the same serum, gave no reactions 



