IMMUNOLOGICAL BEHAVIOR 121 



differed in sexeral respects from the specific antibody of anti- 

 meningococciis serum: It had no atJgkitinins and precipitins for 

 meningococcus; it neutralized the toxic factors of both serologicaf 

 Groups I and III to the same degree; it ^vas capalole of complete 

 neutrahzation in multiple proportions. 



The next step ^^■as to determine ^vhether the high complete 

 neutralization obtained ^\ith the mixtines described 'was due to 

 summation of neutralizing titers of sera making up the mixtures. 



The sera used for the work Avere anti-coli horse serum H„(i Bliss) 

 and tAvo anti-meningococcus sera H7 Bbiso and H7 BL^o- the first 

 having a considerably higher IN titer than the second. 



Inasmuch as 0.1 c.c. and 0.5 c.c. of anti-coli horse serum H,;,, 

 Bliss contained abotit 15 and 45 CN units, respectively, it fol- 

 lowed that, shoidd there be summation of titers, then a mixtme 

 consisting of 0.9 c.c. of anti-meningococcus serum and 0.5 c.c. 

 of serum must have a higher titer than a mixtme consisting of 

 the same amount of the anti-meningococcus serum and only 0.1 

 c.c. of serum H,,,, Bbss- However, t^oth mixtines remained of the 

 same titer. Similarly, in case of simimation of titers, any mixture 

 containing 0.6 c.c. of the anti-coli horse serum should have at least 

 50 neutralizing luiits irresjjective c^f the titer of the anti-menin- 

 gococcus seriun. But. a mixture consisting of 0.4 c.c. of anti-menin- 

 gococcus serum H7 Blis<t and o.fi c.c. of anti-coli horse serum H.jo 

 Bliss gave a CN titer of 115 units, Avhile a mixture consisting of 

 0.4 c.c. of anti-meningococcus serum H7 Bio-,, and 0.6 c.c. of the 

 same anti-coli serum gave no neutralization of 50 units. 



Frcjm the data presented the folloAving cc^nclusions cc:>uld be 

 dra\vn : 



1. The high CN titer of mixtures of anti-meningococcus and 

 anti-coli sera is not due to mere summation of titers of both sera. 



2. The addition of anti-coli serum to anti-meningococcus 

 serum of a \o^v neiUralizing potency does not bring about any 

 increase in potency of the mixture. Moreover, the independent 

 neutralizing potency of the anti-coli serum seems to become abol- 

 ished altogether Avhen mixed Avith an anti-meningococcus serum 

 poor in neutralizing antibodies. 



3. The addition of anti-coli seriun to an anti-meningococcus 

 serum of a high IN titer results in a high CN titer of the mixture. 



These conclusions could be further supported by experiments 

 described below. 



In these experiments there was tested the neutralizing potency 



