124 LOCAL ILSSIL RKAC'IIVLIY 



(iil).iU'(l ;il ;;7 c. loi one hour and injcHlcd inl ra\ cnonsly in a 

 (lose of 'J. ( .('. j)ci kilo ol body \\cii;iu into picj^aicd rabbits. 



Rabbits iiijcdcd intrax fiioiisly with normal iabl)it seriini 

 showed leactions with (oniplctcly neuliali/cd meningococcus re- 

 acting lactois. The etieet was cjiiite striking- since as little as lo 

 iniits ol meningococcus filtrate mixed with 0.9 c.c. oi anti-menin- 

 gococcus serum and 0.1 c.c. ol the auxiliary factor gave reactions 

 in rabbits pre\iously treated Avith normal rabbit serum whilst as 

 many as 100 iniits ot meningococcus filtrate mixed with the same 

 sera gave no reactions in rabbits receiving no preliminary treat- 

 ment with raljfjit serimi. 



Rabbits injected w'ith 0.5 per cent NaCi solution showed no 

 reactions with the neutrahzed mixtures. Moreover, the rabbit 

 serum by itself injected twice within the same intervai of time 

 between injections displayed no reacting potency. Inasmuch as 

 antigen -f-antibody interactions of Ireterologous blood sera in vivo 

 may luring af)out formation of reacting factors (Chapter ix) , rab- 

 l^its were eacli separately injected with rabbit and normal human 

 sera, rabbit and normal horse sera and with rabbit and immune 

 horse sera, respectively. No reactions ^vere elicited by these sera 

 in prepared sites. 



The treatment of rabbits with the rabbit serum did not raise 

 the susceptibility to the toxic filtrates alone. 



From the foregoing experiments it was concltided that the pre- 

 liminary intravenotis injection of the rabbit serum induced reac- 

 tivation of completely neutralized meningococcus reacting factors. 

 The reactivating property of the serum was titrated in a twofold 

 manner: 



1. Prepared rabbits were injected intravenously with the same 

 amoimt of the rabbit serum {i.e., 1 c.c. of undiluted rabbit serum 

 per kilo of body ^veight) , and divided into a ninnber of groups 

 of 3 each. One-half hotn- later rabbits of each group received a 

 single intravenous injection of a mixture of a varying ninnber 

 of toxic iniits mixed with a constant amount of immune serum. 

 In these experiments untreated rabbits showed no reactions ^vith 

 120 neutralized reacting units, w^iilst the treated ones gave reac- 

 tions with 25 and no reactions with 10 neutralized reacting units. 

 Thus, the smallest amount of neutralized reacting factors showing 

 no reactions in treated rabbits Avas apj^roximately 17 units. There 

 was obtained, therefore, reactivation of six-sevenths of the neu- 

 tralized reactinii factors. 



