IMMUNOLOGICAL BEHAVIOR 



lor. 



consistent neutrali/ations \vith Ty 159 stock reactin" factors, al- 

 though fixing a liigh degree oi irregular neutralization. The re- 

 maining 2 stock strains occtipied interniediate positions in the 



degree of consistent neutralizations, one (Ty 8G4 stock) being of 

 lower neutralizability than the other (Ty 157 stock) . The strains 

 preserved the same differences Avhen tested with the polyvalent 

 horse serum (Horse.-, Bleedingi^) . The present tentative expla- 

 nation of these findings is as follows: 



The reacting factors of the strain showing the highest degree 

 of neutralizability appear to be the simplest in their antigenic 



