IMMUNITY TO LOCAL SKIN REACTIVITY 1 37 



the phenomenon. Reactions could ])e, howe\er, elicited in ad- 

 joining skin sites. 



Parallel to my obseixations on acqiurement of non-specific ac- 

 ti\ e immunity l)y certain rabbits follo^ving■ the repeated reproduc- 

 tion of the phenomenon, Peck and Sobotka (1931) studied the 

 production of the refractory state of the phenomenon follo^ving 

 injections of \enom of the moccasin snake. In their preliminary 

 Avork they assmned that animals de\eloping intense pinpina fob 

 lo^ving the intracutaneous injection of snake \enom in dilutions 

 of 1:1000 and 1:2000 are more likely to sho\v the phenomenon 

 of local skin reactivity than those giving a ^veak reaction with 

 snake \enom. After a period of fourteen days to one month 

 elajDsed bet^veen the time of grading \vith \enom and the produc- 

 tion of the phenomenon of local skin reacti\ ity, a large number 

 of rabbits became refractory to the phenomenon. An incubation 

 period of not less than fourteen days ^vas necessary for the de- 

 velopment of this resistance. The incidence of refractory animals 

 appeared to be within limits inversely proportional to the amount 

 of active principles injected intravenously for the elicitation of 

 the phenomenon. The intra\enoiis injection of moccasin \enom 

 proved most efficacious in developing refractoriness, although the 

 intradermai and intraperitoneal injections ^vere also successful. 

 The refractory state Avas also stili present forty-four days after 

 the primary injection of the moccasin \enom. The refractory ani- 

 mals did not show any changed reaction to the local effect of 

 moccasin venom in the concentration used. No circulating anti- 

 bodies could be demonstrated to explain the refractory state. 

 Passive immunization ^vith anti-venom had no effect on the course 

 of the phenomenon of local skin reactivity. The authors con- 

 cluded that the phenomenon of local skin reactivity probably de- 

 pends on induced vulnerability of the capillaries (at the site of 

 primary injection) to subsequent injection of bacterial filtrates. 

 They assumed, therefore, that the injection of small quantities 

 of vascular poison produces a change in the capillaries ^\•hich raises 

 the threshold for the elicitation of the phenomenon of local skin 

 reactivity. The refractory state induced by venom is apparently of 

 a cellular nature, inasmuch as passi\e resistance could not be 

 elicited by the use of serum from rabbits made refractory by means 

 of the phenomenon or by injections of anti-\enom. 



In further experiments Peck (1933, 1934) found that the re- 

 fractoriness to the phenomenon could not be produced by im- 



