DISSOCIATION AND TRANSFORMATION 157 



a killed Type IIS strain obtained a typical IIS pneumococcus. Not 

 all the R variants could be reverted. 



Somewhat less success in this respect attended the efforts of Rei- 

 mann. 1129 The R strains evolved by immune serum-broth cultivation 

 were as a rule irreversible, only one of many strains passing back 

 to the S form of Type I or over to Type III, the reversion depend- 

 ing upon the type of the heated culture used. No transformations 

 to Type II occurred, although in one instance it appeared that a 

 heated IIS culture induced the reversion of the R strain to the 

 Type IS prototype. Reimann obtained positive reversions of typi- 

 cal R forms from pneumococci of Types I or II when he inocu- 

 lated the R strains subcutaneously into mice with heated S cul- 

 tures of Types I, II, and III. The living IR culture plus heated 

 Type IIS vaccine gave Type IIS pneumococci ; IIR became IS or 

 HIS, depending upon the type of heated culture used. Both Types 

 IR and IIR, when inoculated with heated cultures of homologous 

 type S forms, frequently reverted to the respective prototypes. 

 These seemingly bizarre biological changes were, therefore, becom- 

 ing a routine laboratory performance. 



Baurhenn's 93 efforts at reversion (1932) were more fruitful than 

 Reimann's. By subculturing R strains with homologous and heter- 

 ologous vaccines consisting of heat-killed cultures, he changed the 

 R strains into their original S forms and to the S form of a differ- 

 ent type. Baurhenn inclined to Griffith's view that all pneumococ- 

 cal types possess a common basic form. The basic form, under the 

 stimulation of the activating principle, responds by acquiring the 

 properties of the activator. Baurhenn claimed to be the first to 

 have produced transformation within Group X (Group IV) as 

 well as the transformation of a fixed type (I, II, or III) into a 

 specific type of Group X. This feat is, of course, entirely possible, 

 and from what we already know of the phenomena of transforma- 

 tion, there is no reason to doubt that similar changes may occur 

 in the case of all the known types of pneumococci. 



Dawson (1928) 2 " confirmed and expanded Griffith's observa- 



