822 AGGLUTININS AND THEIR APPLICATIONS 



degree of agglutination at 1/50 dilution of serum as positive. In dourine' the test is 

 of value. 



For the identification of bacterial species the reaction of agglutination and agglu- 

 tinin absorption is more widely applied than for any other purposes. Differences at 

 present undetectable by an examination of morphological or cultural characteristics 

 are readily manifested. The finding of distinctive subgroups or strains among a great 

 many species is the rule rather than the exception. Thus pneumococci and menin- 

 gococci are each separable into groups or types. That this finer differentiation is of 

 more than academic interest is attested by the fact that the identification of the 

 group to which the infecting micro-organism belongs has an important bearing upon 

 the choice of serum used in therapy. The toxin elaborated by the various serological 

 strains of B. tetani and C. diphtheriae are apparently neutralized, respectively, by 

 tetanus and diphtheria antitoxin obtained by immunization with the toxin of any 

 one strain. However, this is not true in the case of B. botulinus. The members of one 

 group produce a toxin which is not neutralized by an antitoxin common to another 

 group. 



BACTERIAL VARIATION AND AGGLUTINATION 



One cannot evade the puzzling and very disconcerting problem of bacterial varia- 

 tion or dissociation in its bearing on the application of the phenomenon of agglutina- 

 tion. "The bacteriologist nowadays has not only to define the species of bacterium 

 with which he is dealing, but also the particular form or variant."^ One must tread 

 lightly and with great caution on the new ground which is being opened for explora- 

 tion. Certain facts have apparently been established in certain groups of micro- 

 organisms. Schiitze^ and Arkwright'^ have described "rough" variants among the 

 dysentery and Salmonella groups, which behave in a characteristic fashion. The R 

 ("rough") form from strains of B. dysenteriae (Shiga) agglutinates spontaneously in 

 0.85 per cent sodium chloride solution. Agglutination tests, however, may satisfac- 

 torily be carried out with weaker solutions (0.4-0.1 per cent). The S ("smooth") 

 form makes a stable suspension in 0.85 per cent saline. The S form on agglutination 

 yields large clumps; the R, small clumps readily shaken up into a turbid suspension. 

 Further, the two forms differ very markedly in their agglutinating, antigenic, and 

 absorbing properties. The S forms obtained from different strains of B. dysenteriae 

 (Shiga) resemble one another serologically, but are distinct from all the R forms; and 

 the R forms of different strains appear to have little relation to any S forms, but to be 

 closely related to one another. The striking fact is that there has apparently been 

 revealed a difference in antigenic properties of R and S cultures, both of which were 

 isolated from the same parent culture. Goyle^ undertook to investigate the sero- 

 logical relationship between B. typhosus and B. enteriditis and to discover to what 

 extent the H and O forms of Weil and Felix'' and the S and R forms described by Ark- 



' Watson, E. A.: Dom'niion of Canada Depl. ofAgn'c, Ileallh of Animals Branch. 1920. 

 * Arkwright, J. A.: loc. ril. ■' Arkwright, J. A.: op. cit., 24, 36. 1921. 



3 Schiitze, H.: /. //v.?., 20, 330. u)2i. s Go3-lc, A. N.: ./. I'alli. 5" Bad., 29, 149. 1926. 



''Weil, E., and Felix, A.: /Jsclir.f. I nnniinitiilsfoyscli. 11. e.xper. T/ierap., Abt. I, Orig., 29, 24. 

 1920. 



