I 2() LOCAL ILSSUE REACTIVITY 



latter coniparison (Icnioiistralcs. tlu'ictore, a 'imiliiplc jjiopor- 

 tioii" neutiali/ation similar lo thai obtained in B. lyjjho.sii.s ex- 

 })crinients. These cliscre|)ancics suggested the possibility tliat 

 there may exist a factor in the serum which aids the neutraliza- 

 tion and being present in insufficient amounts in 0.25 c.c, the 

 neutralization is not brought out fully until a sufficiently large 

 amount of serum is used which can supply this factor. The experi- 

 ments described below deal with this problem.^- 



AN ANTnU)!)^ AUXII.IARV TO SERUM NEUTRALIZATION OE 

 MENINGOCOCCUS REACTING FACTORS 



Studies on meningococcus brought out the fact that certain 

 anti-meningococcus sera of a \o\v CN titer possessed a high IN 

 titer. Moreover, if multiples of 0.25 c.c. ^vere used, the CN titer 

 did not increase proportionately ^vhilst there Avas observed a 

 roughly jjroportionate increase in the IN titer. It seemed possible 

 that the inability of anti-meningococcus sera to neutralize com- 

 pletely the toxic factors in midtiple proportions may be due to 

 the lack of the hypothetical auxiliary factor assumed to exist in 

 B. coli sera just discussed. A search for this hypothetical auxil- 

 iary factor was done by studying the neutralization of meningo- 

 coccus reacting factors by means of mixtures of anti-meningo- 

 coccus sera 'with heterologous immime sera which by themselves 

 Avere capable of complete neutralization in midtiple proportions 

 of their homologous toxic sidjstances. It ^vas foinid, thus, that the 

 mixtures of anti-meningococcus horse sera with anti-coli horse 

 sera displayed a remarkable neutralizing potency. First, these mix- 

 tures exhibited a substantial increase in the IN titer; second, they 

 showed complete neutralization of large numbers of toxic units; 

 and, third, they differed in their potency for filtrates of various 

 serological groups. 



It was possible to determine the CN titers of the mixtines. 

 Thus, if a given mixtine neutralized completely 100 reacting 

 units and only irregularly 130 units, the CN titer Avas considered 

 approximately 115 units. The CN determinations, as above men- 

 tioned, are considerably more accurate than the IN titrations. 



Data were also obtained on the reciprocal quantitative relation- 

 ships between the anti-coli and anti-meningococcus horse sera. 

 In the examples studied the anti-coli horse serum Avas by itself 

 capable of giving complete neutralization of meningococcus re- 

 acting factors. The neutralizing property of this serum, hoAvever, 



