140 LOCAL TLSSUE REACTIVITY 



traxcnously alter xarioiis inter\als oi time (one lo lurly-eight 

 hours) . No lvj)i( al reactions were obtained. 



Sohel in my laboratories attempted without success to repro- 

 duce the phenomenon in "white rats by means of combined intra- 

 dermal and intravenous injections of enorm(nis doses of B. ty- 

 phosus, B. paratypJwsus and meningococcus "agar ^vashings" 

 filtrates of ascertained potency. 



In 1929, I observed the phenomenon in 2 goats with B. ty- 

 pliosns tryptic digest broth fikrate and in one horse with menin- 

 gococcus "agar Avashings" hltrate. 



PASSIVE IMMUNITY TO ACTIVE PRINCIPLES 



The problem of passive immunity to the phenomenon was 

 studied with B. typhosus active principles (Sh^vartzman, 193 id). 

 The skin of rabbits was prepared by a single injection ^vitii 0.25 

 c.c. of the toxic filtrate. After various intervals of time the pre- 

 pared rabbits received an intravenous injection of serum fol- 

 lowed by an intravenous injection of the toxic filtrate. The toxic 

 filtrate ^vas injected t^venty-four hours after the skin injection of 

 the hltrate. The interval of time between the intravenous injec- 

 tion of the serum and the folloAving intra\enous injection of the 

 ftltratt: varied, but in most experiments it was one-half hour, 

 and in some experiments one and one-half and t^vo and one-half 

 hours. Reactions were obtained in only i().() per cent of rabbits 

 passi\'ely protected by the immune serimi. Ninety per cent of non- 

 protected rabbits showed reactions ^vith a reacting dose even 

 smaller than the one employed in the serum-protected group 

 (dilution 1:10 in the control group and dilution 1:8 in the ex- 

 perimental group) . Thus, it became at once e\'ident that it is 

 possible to elicit passive immunity to B. typJwsus reacting factors. 



In additional experiments the protective potency of the im- 

 mune serum against B. typJiosus reacting factors was titrated. 

 Anti-typhoid horse serum Avas injected intravenously into pre- 

 pared rabbits one-half hour prior to the intravenous injection of 

 B. typliosiis filtrate. Rabbits protected ^vith various amounts of 

 the serum were tested against various numbers of reacting units. 

 The largest number of reacting units giving no reaction in all 

 rafjbits tested was used to compute the /// vivo potency of a given 

 amount of serum. Thus, if 2 c.c. of a certain seruin injected in- 

 travenously per kilo of body weight, protected all rabbits tested 



