IIO LOCAL TLSSUE REACTIVITY 



{()iisi(lcial)lc iiulix idiial xariations ol tlie la])()rat()ry animals in 

 response to the effect ot the colcHi-typhoid gronp. It could be 

 safely assumed from these experiments that the passage of the Ty 

 Tl stock strain through mice did not increase its virulence. It 

 was clear, therefore, that the change in the neutralizability of the 

 reacting factors which occurred in the mouse strain ^vas not re- 

 lated to its virulence. 



There \\as, ho^vever, unquestionable lower virulence on the 

 part of the rough variants of B. typliosns, as compared to the 

 virulence of the stock strains from which they were derived. This 

 was previously observed for the colon-typhoid group by Topley 

 and Aryton, Jordan, Orcutt, White, Goyle, Schiitze, and others 

 quoted by Hadley (1927) . The lo^vering of virulence was coinci- 

 dent with a change in the neutralizability of the "rough" react- 

 ing factors by anti-stock sera. Ho^vever, there Avere differences in 

 the neutral izal)ility of the reacting" factors derived from the t^V() 

 "rough" variants by anti-rough sera. No differences could l)e 

 recognized in the virulence of these rough variants. 



Thus, it may be concluded that the active principles of B. ty- 

 pJiosiLS and B. coli possess a clear-cut strain and variant specificity. 



By the "strain" specificity is meant the fact that various strains, 

 chosen at random, of a given species of bacteria produce reacting 

 factors Avhich differ in their neutralizability. The differences are 

 explainable on the basis of various degrees of antigenic com- 

 plexity. 



The "variant" specificity is demonstrated l)y a luunber of facts. 



The passage through mice induces in certain strains a partial 

 loss of neutralizability of reacting factors. This is probably due 

 to variation to^vards smoothness Avith an increase in the antigenic 

 complexity. As a matter of fact, the reacting factors of a strain 

 . considered as the simplest in their structine imderwent a partial 

 loss of neutralizability after passages through mice, ^vhilst the 

 neutralizability of reacting factors of a strain found to be the most 

 complex before the passage through mice ^vas not influenced by 

 the latter procedure. The other type of "variant" specificity is 

 conditioned by the change of a strain into rough. The "rough" 

 reacting factors acquire a new specificity. 



The above described changes in the neutralizability of the re- 

 acting factors taken together cannot be consistently correlated 

 ^vith colon morphology, serum agglutinability and virulence of 

 strains, nor with the serum precipitability of the culture filtrates. 



