1()(S LOCAL riSSLE REACTIVITY 



Serum agglutinability of various stock strains and variants of 

 B. typhosus and the neutralizability of reacting factors: 



These tests ^vere performed in the usual manner, except tliat 

 0.2 1 per cent NaCl sohuion was used for making serinn dihi- 

 tions for the aggliuination of the rough variants. The gro^\th of 

 rough \ariants on solid media used for the tests was suspended 

 in distilled ^vater, ^vashed by centrifugalization and resuspended 

 in 0.2 1 per cent NaCl solution. Tiie results of the agglutination 

 tests ^vith various cultmes bring out the follo^ving: 



Two modes of comparison of agglutinability of various strains 

 by immune sera were used: (a) the agglutination titer, namely, 

 the hiohest flilution of the serimi ^vith which agglutination is 

 obtained, and (b) the degree of agglutination in various dilu- 

 tions of sera. The agglutination titer of the stock strains could 

 not be correlated with the degree of neutralizability of reacting 

 factors deri\'ed from the same strains. For instance, the agglutina- 

 tion titer of Serimi S.-, was the same for Ty Tl stock and Ty 159 

 stock strains, ^vhilst there ^vas consistent neutralization of 26 re- 

 acting units of the first and no consistent neutralization of the 

 latter strain. In another example, the reacting factors of Ty 157 

 stock strain "were neutralized by serum Horse.-, Bleedingiu to a 

 higher titer than those of strain Ty 864 stock, but the agglutina- 

 tion titer ^vas higher for the second than for the first strain. Con- 

 versely, it appeared that the degree of agglutination obtained in 

 various dilutions of sera w^as an indication of differences in neu- 

 tralizability of stock strains of B. typJiosus. Thus, shoidd one ar- 

 range the strains in order of their comparati\e neiuralizability 

 and in order of the intensity of agglutination in low dilutions of 

 sera the same order is obtained for both. i.-Ty Tl stock, 2.-Ty 

 157 stock, 3.-Ty 864 stock, and 4.-Ty 159 stock would fall in this 

 order. The above described observation is to be differentiated 

 from previously reported results showing that the agglutinating 

 and neutralizing antibodies do not run parallel in immune sera. 



The loss of agglutinability due to passage of strains through 

 mice was not an indication of a change in the neutralizability of 

 the reacting factors. For, on the one hand, there ^vas the exam- 

 ple of the Ty Tl mouse strains Avhich, after passage through mice, 

 produced reacting factors of louver neutralizability ^vithout change 

 in agglutinability. On the other hand, in contrast to this strain. 



