83 



As shown by its negative agglutination reactions with the other 

 sera the strain Lister 3 is almost free from the II and III 

 components : the strains Self 1, L 10, and L 36a are pure II, 

 and the strain B.S. 6 contains only traces of I and II antigens. 



But the strains Fechger and S 1, while containing the I 

 antigen in greater amount than II or III, yet do not contain 

 it as the predominating component. Fechger produces a serum 

 agglutinating none of the other eleven strains to a significant 

 degree (it picks out a few from the larger collection of strains 

 from pneumonia, &c). Its main antigen is evidently different 

 from I, II, and III. 



Rosenhain and L 45 react with both Lister 3 and the II sera, 

 i.e., they contain both I and II antigens in significant amounts. 



S 1 reacts with the sera of both Lister 3 and B.S. 6, i.e., it 

 contains a certain amount of both I and III components, but 

 its serum agglutinates the other eleven strains hardly at all. 

 Like Fechger, it evidently possesses another quite different 

 antigen as the predominating constituent, and its serum similarly 

 fails to agglutinate decisively the other strains except S 4 : it 

 agglutinates well, however, a few strains isolated from other 

 cases of catarrhal pneumonia and, as will be seen, may represent 

 an epidemic type. 



Fleming, though its II component is strongly marked, has 

 affinities with B.S. 6 and L 1a, i.e., it contains also some of the 

 III antigen. 



L 1a, though the III component predominates in it, has 

 quite significant amounts of both I and II and, accordingly, 

 its serum, though a strong III agglutinator, definitely agglutinates 

 both Lister 3 and L 10. 



S 4 does not agglutinate strongly with any but its own serum 

 and its serum fails to agglutinate any of the other strains except 

 SI. Its affinity to S 1 is further indicated by the fact that S 3, 

 a strain isolated from a case of influenzal pneumonia in the same 

 locality, is agglutinated by both S 1 and S 4 sera and by these 

 alone. 



If one assumes that these twelve strains are at all repre- 

 sentative of the influenza bacillus as a species, it is evident that, 

 though it is possible to differentiate certain antigenic components, 

 yet the species has as its most pronounced serological feature a 

 great diversity in antigenic character. 



Absorption of Agglutinin. 



The three antigens indicated by the cross-agglutination tests 

 as being fairly widely distributed in the species are readily 

 demonstrable by the test for absorption of agglutinin. In fact, 

 in the majority of cases in which agglutination occurs with the 

 formation of permanent clumps visible to the naked eye, it is 

 possible to show that contact with the agglutinable bacillus 

 removes agglutinin from the serum, i.e., that an antigen is present 

 in the aggluinated strain similar to one present in the strain with 



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