THE SENSITIZERS OF SERA. 257 



In the first two tubes a marked cloudiness appeared, which was 

 lacking in tube 3. In these two first tubes the fixation of alexin 

 also was complete, but there was none in tube 3. The serum of 

 rabbits injected with deftbrinated hen blood is capable of precipitating 

 and of sensitizing hen-egg white as well as rabbit > egg serum. 



Is the converse true? That is to say, will rabbit > egg serum 

 agglutinate and sensitize hen blood corpuscles? The experiment 

 to answer this question contains three tubes: 



Tube 1 Washed hen corpuscles 0.1 c.c. 



S. normal rabbit, 56 degrees 0.3 c.c. 



Rabbit alexin 0.2 c.c. 



Tube 2 Washed hen corpuscles 0.1 c.c. 



S. rabbit > egg, 56 degrees 0.3 c.c. 



Rabbit alexin 0.2 c.c. 



Tube 3 Washed hen corpuscles 0.1 c.c. 



S. rabbit > hen blood, 56 degrees 0.3 c.c. 



Rabbit alexin 0.2 c.c. 



There is no hemolysis in tube 1 and rapid hemolysis in tube 3; 

 in 2, hemolysis occurs, but slowly, and apparently is not accom- 

 panied by agglutination. 



We then determined whether this rabbit > egg serum would act on 

 normal hen serum; there was no effect. In a similar manner rabbit 

 > milk serum has no effect on cow serum. In short, it is evident 

 that if an immune serum is tested on elements other than those used 

 for immunization, but from the same animal species, the results 

 vary and cannot be prognosticated in an untried combination. 

 Although rabbit > milk serum has no effect on cow serum and 

 rabbit > egg serum none on hen serum, we find that rabbit > 

 egg serum will sensitize hen corpuscles to a certain extent, and 

 that rabbit > hen blood serum is very active against hen-egg white. 



Conclusions 



These experiments would, we believe, lead to the conclusions: 

 1. That in the sera obtained by injecting rabbits with large 

 closes of cow milk, egg white, pure horse fibrinogen, or heated dog 

 serum there are, in addition to the precipitins of Bordet and 

 Tchistovitch, substances analogous to the sensitizers described by 

 Bordet in bacteriolytic and hemolytic sera, and later found in the 

 majority of antimicrobial sera. The same is true in respect to the 



