144 LOCAL TLSSUE REACTIVITY 



(iiiieiuc ol the skin reaction could be j)re\ente(l by serum in- 

 jection ii it followed the injection of the filtrate. The reactions 

 were inhibited by an intravenous injection of serum following 

 the injection of reacting factors, provided the serum dose was very 

 large and provided the injection of serum ^vas made immediately 

 after the filtrate injection. The skin reaction coidd not be pre- 

 vented it the inmiune serimi was injected twenty minutes or 

 longer after the injection of reacting factors. The results are most 

 likely due to fixation of the reacting factors in the prepared tis- 

 sue shortly after their introduction into the general circulation. 

 As a matter of fact, this can be expected, since even one hour 

 after the intravenous injection of the toxic filtrate one can see a 

 blue discoloration at the prepared skin sites, although it takes 

 fotu" to five hoins for the fidl development of hemorrhagic 

 necrosis. 



RECAPITULATION 



Rabbits differ in the degree of susceptibility to the phenome- 

 non of local skin reactivity. Approximately 20 per cent of rab- 

 bits sho^v a high degree of refiactoriness to B. typhosus active 

 principles. With sufficiently large doses of meningococctis the 

 phenomenon may be produced in all the adtilt rabbits tested. A 

 high percentage of new-born rabfjits are refractory to the phe- 

 nomenon. 



The idea of possible existence of spontaneous specific im- 

 munity to the phenomenon is brought otit by the experiments 

 in Avhich rabbits prepared by simultaneotis injections of B. ty- 

 pJiosus, B. coli, and meningococcus filtrates and injected intra- 

 venously with the active principles sho^v. in some instances, reac- 

 tions in all sites and in others only in one or t^vo sites. 



Immunization of rabbits with bacterial filtrates induces active 

 immunity to the phenomenon. The specificity of this immunity 

 may be tested with graded amounts of active principles. Two 

 types of response follo^v immunization. 



1. Specific immunity \vhich is obtained in rabbits highly sus- 

 ceptible to the phenomenon. 2. Non-specific immunity ^vhich is 

 elicited in rabbits ^vith partial spontaneous immunity. 



There is suggestive evidence that non-specific immunity may 

 be obtained in a certain percentage of rabl)its through immuniza- 

 tion \sTth certain snake venoms. 



