178 BIOLOGY OF PNEUMOCOCCUS 



During the dissociative process antigenic action may vary from 

 one of strict type-specificity to one merely of the broader species- 

 specificity. Degraded forms may, if the degenerative process has 

 not been complete, regain all their original morphological, cul- 

 tural, and immunological characters. Regeneration can be accom- 

 plished by rejuvenating the strain by passage through a suscep- 

 tible animal, by cultivation in media containing an antiserum 

 produced by immunization with the degraded forms, or through the 

 stimulus afforded by heat-killed virulent cultures of an homologous 

 type. Degraded variants, moreover, can by the action of devital- 

 ized, virulent pneumococci, actually be transformed into pneumo- 

 cocci of types entirely different from those from which the variants 

 were derived and identical with those of the cultures stimulating 

 transformation. The nature of this transformative or mutative 

 principle is still unknown, but it is probable that it is a constituent 

 of the pneumococcal cell and not an extracellular product of its 

 metabolism. 



The broader transmutation of Pneumococcus into Streptococ- 

 cus and of Streptococcus into Pneumococcus has been advanced as 

 a biological possibility. Experiments have been described in which 

 it was alleged that this transmutation took place. Not only has it 

 been claimed that both virulent and degraded pneumococci were 

 converted into avirulent Streptococcus viridans, but the organisms 

 were said to have become virulent hemolytic streptococci, while the 

 streptococcal forms have been further changed into pneumococci. 

 Such radical departures from established theory require the clos- 

 est scrutiny of the evidence advanced and of the accumulation of 

 new and confirmatory facts before they can be accepted. 



