IMMUNOLOGICAL BEHAVIOR 95 



proved that the fihrate "A7" did not suffer any change in potency 

 during the tA\o months in \vhich this \vork \vas carried out. 



One area of the skin of the aljdoniinal Aval I of a rabfjit Avas in- 

 jected Asith 0.25 c.c. of tlie luidihued hhrate "A7" or 0.25 c.c. of 

 the filtrate previously diluted 1:4. Twenty-two to twenty-four 

 horns later a single intraxenous injection of the filtrate, or of a 

 mixtine of the filtrate with a given serinn, Avas made. The mix- 

 tines prepared on the morning of the experiments, as Avell as the 

 filtrate alone were incubated in the water bath at 37" c. for one 

 hour. The precipitate in the mixttnes Avas broken up by shaking 

 immediately before the injection. The readings of the reactions 

 were made foiu" and one-half horns after the intravenous injec- 

 tion. A rabbit was recorded "positive" Avhen the prepared area of 

 the skin showed severe hemorrhagic necrosis. "Doubtful" rabbits 

 were those shoAving mild pimctiform hemorrhagic areas of dark 

 red appearance. 



In the "negative" rabbits, no reactions were seen. Some of the 

 rabbits died in the course of the four and one-half hotus follow^- 

 ing the intravenous injection. Their deaths were noted. If the 

 dead rabbits showed no reactions or a diffuse discoloration of the 

 skin, no readings were recorded in the protocols. When, how- 

 ever, there Avas observed a Avell-defined reaction, the result Avas 

 noted. 



The basic experiments carried otu in the manner described are 

 sinnmarized in Table ni. 



Inasmuch as the neutralization experiments Avith each serimi 

 were followed by a control group of rabbits receixing the same 

 skin and intra\enotrs doses of the toxic filtrate alone (Avithout im- 

 miuie serum) , it was possible to establish the fact that in the ab- 

 sence of immtme serinn about 95 per cent of the surxiving rabbits 

 gave severe hemorrhage reactions. On the other hand, 30 rabbits 

 Avhich received a mixtine of the same amoinit of the filtrate with 

 some batches of imminie sera, showed no reactions. Thus, the ex- 

 periments established beyond question the fact that B. h'jjliosus 

 reacting factors can be neiUralized by imminie serimi. 



WHien a mixture of the filtrate with the immune serimi (Horse 

 4) previously diluted 1:5 Avas injected, there were obtained re- 

 actions in 3 rabbits out of seven. If the high j^ercentage of posi- 

 tive results obtained in the control group is kept in mind, it 

 becomes evident that the 1:5 diluted serum produced neutraliza- 

 tion of the reacting factors but did so irregularly. The irregularity 



