PHILIP HADLEY 93 



been followed by Webster into lines of considerable interest. The study of Theobald Smith 

 and Gladys Bryant' on a "mutating" form of B. coli may also be mentioned as an instance 

 dealing with the dissociative reaction, although the authors did not emphasize the relation. 

 Gratia at an earlier date had made somewhat similar, though less detailed, observations on 

 the same species. The chief results of all of these studies have been to demonstrate with ever 

 increasing clearness the new characteristics possessed by the recognized variants; also to 

 validate many earlier observations of a similar nature, but manifestly concerned with the 

 same phenomenon. In addition, the more recent studies, besides depicting the S and R forms, 

 have presented evidence for the existence of the third significant culture type, the O form 

 (intermetliate), also recognized by earlier workers, lying as a transitional form between S 

 andR. 



COLONIAL, CULTURAL, AND MORPHOLOGICAL ASPECTS 

 OF MICROBIC DISSOCIATION 



As has already been pointed out, microbic dissociation manifests itself in varia- 

 tions in colony form, in cultural growth, in comparative cytology, in cell morphology, 

 in biochemical reactions, in immunological reactions, and in virulence. In the present 

 section we shall consider some of the details relating to the first three of these points, 

 with the attempt to indicate that the variations and correlated characters observed 

 are not the result of chance, but depend on certain laws governing the transformations 

 in widely separated bacterial species.^ 



1 COLONIAL ASPECTS 



As Firtsch^ clearly suggested by his remarkable study of variation in V. protcus 

 in 1888, colonial variation is the most fundamental, consistent, and clearly observed 

 phenomenon in dissociative variation. Each bacterial species possesses, not one "nor- 

 mal" colony form, but a variety, each of which one must be able to recognize before 

 he can affirm that he knows the "species." Each of these forms is determined by the 

 stage of cyclogeny attained by the individual cells that comprise the colony structure. 

 The time is now past when similarity in colony form must be taken as evidence of the 

 close relationship of the organisms contained; or when dissimilar colony types must 

 be regarded as indicating unrelated species. The fact of the matter is, that the de- 

 gree of variation in colony form in one and the same species may be, and usually is, 

 greater than the degree of variation in colony form of equivalent cyclostages of clearly 

 distinct species. The diverse colony forms observed within pure lines of B. subtilis 

 (Soule),4 of B. anthracis (Preisz,^ Wagner, Nungester*), of hemolytic streptococci 

 (Cowan),'? of S.fecalis (Faith Hadley),^ of the meningococcus and gonococcus (Atkin),^ 



' Smith, T., and Bryant, Gladys: /. Exper. Med., 46, 133. 1927. 



^ It is impossible to consider the biochemical, serological and immunological aspects within the 

 limits of this chapter. 



3 Firtsch, G.: loc. cit. 



'•Soule, M. S.: Jour. Inject. Dis. 1928, No. 2. 



5 Preisz, H.: Centralbl.f. Bakteriol., Abt. I, Grig., 35, 280. 1904; also 53, 510. ign. 



'Nungester, W.: Proc. Soc. Exper. Biol, b' Med., 24, 959. 1927. 



'Cowan, Mary: loc. cit. 



* Personal communication. 



' Atkin, E. E.: loc. cit. 



