DISSOCIATION AND TRANSFORMATION 147 



S forms to avirulent R forms with their subsequent destruction by 

 phagocytosis. In a still later study 1129 it was noticed that daughter 

 colonies frequently appeared among the R variants, and in some 

 instances tended to replace the typical R forms. The daughter 

 strains grew in colonies with glistening surface, morphologically 

 indistinguishable from genuine S colonies, although the characters 

 of the bacteria comprising the daughter colonies conformed to the 

 R variety. Strains of R pneumococci, which had seemed irreversi- 

 ble, were apparently converted into the S form when treated by the 

 method of Griffith, that is, by growth in specific immune serum. 

 Reimann considered that recent experimental studies indicated 

 that virulent S pneumococci might dissociate into the R form in 

 vivo, that R forms occasionally could be found in the sputum of 

 pneumonia patients, and also might live dormant in vivo for a con- 

 siderable period of time. 



The recovery of R variants from the body has recently been re- 

 ported by Shibley and Rogers. 1262 Twenty-four lung punctures 

 made in lobar pneumonia patients at the time of crisis or lysis 

 yielded R forms of pneumococci in all but four cases. 



DETAILS OF COLONY FORMATION 



Dawson 299 maintained that colony morphology alone could not 

 be considered as a final criterion of dissociation ; it should be con- 

 firmed by specific agglutination and virulence tests. While it was 

 possible, by mouse passage, to accomplish a complete reversion of 

 Type IIR to Type IIS, it was not possible to convert the particu- 

 lar Type IR strain studied to the corresponding S form. In the 

 case of a Type IIIR strain, it required twenty-eight mouse pas- 

 sages to restore the variant to its original S condition. Growth of 

 the same R strains in broth containing 10 per cent anti-R serum 

 resulted in reversion of Type IIR on the fifth transfer, of Type 

 IIIR after eight to twelve transfers, but failed to affect the Type 

 IR. Dawson thought that the reversion of R to S did not depend 



