26 LOCAL TISSUE REACTIVITY 



of a moderate ainouiil ol reacting fa( tors is made through the 

 marginal vein oi one ol tlie |)rej)ared ears, it may be reason- 

 al)l\ c\j)c'(lc(l lliat most ol iliat material is fixed in the prepared 

 ear and only an excess readies the other sites prepared. This pos- 

 sibility was a])parently resjionsil)le for the highly (onfusing re- 

 sults of titrations rej)orted in the first part of Palost and Branhams' 

 paper. 



Method II: Titrations of skin-preparatory factors against con- 

 stant intravenous doses: 



Titrations of skin-preparatory factcMS against constant intra- 

 venous doses consisted of a single intradermal injection of a 

 hltrate undiluted and in various dilutions. Groups of 3 to 5 rab- 

 bits were ordinarily used for each preparatory dose. Twenty-four 

 hours later the rabbits of all the groups received the same intra- 

 venous dose. This may be illustrated as follo^vs: (Shwartzman, 



1930^^. i935«) • 



Protocol 13 : B. typhosus "agar washings" filtrate was used for a single 

 intradermal injection. The following dilutions were prepared: 1:5, 1:10, 

 1:30. i:()o, 1:120, 1:200, and 1:300. Three rabbits were prepared with each 

 dilution. Twenty-four hours later, 1 c.c. of a dilution 1:10 of the same fil- 

 trate, per kilo of body weight, was injected intravenously. Following the in- 

 travenous injection, 2 to 3 rabbits of each of the groups receiving dilutions 

 up to 1:60 reacted with severe hemorrhagic necrosis. Only 1 to 2 rabbits 

 of the groups prepared with dilutions 1:120 and 1:200 gave positive reactions. 

 Dilution 1:300 gave no reactions. 



On the ])asis of the above typical experiment, it may be stated 

 that the titers of the skin-preparatory factors can be fairly ac- 

 curately determined. 



If the residts of this type of titration are compared ^vith the 

 reciprocal titration, it becomes obvious that a considerably smal- 

 ler amount of reacting factors is required in older to elicit reac- 

 tions in one site than Avhen several sites are prepared (approxi- 

 mately ten times less) . This again is taken as further proof as to 

 the reciprocal relationships f^etween the intradermal and intra- 

 venous doses necessary for the elicitation of the phenomenon. 



Method III: Titration of reacting factors against constant 

 skin-preparatory doses : 



The quantitative measurement of the reacting factors is con- 

 veniently carried out as follows: 



