150 BIOLOGY OF PNEUMOCOCCUS 



pictures could be obtained for pneumococci as for streptococci, 

 but was not sure how far the bactericidal action of the body fluids 

 or how far bacteriophagic action were to be considered as the basis 

 for the phenomena. 



Farago (1932) 390 investigated the possible participation of bac- 

 teriophagic action in the dissociative processes, but decided that it 

 was not a factor. He objected to the designation R and S for dis- 

 sociants, because secondary colonies were formed from virulent or- 

 ganisms, whereas Griffith's R modification arose from avirulent 

 strains. It is difficult to follow Farago's reasoning, but it may be 

 possible that he had in mind some of the features later described 

 by Dawson. 



ANTIGENICITY OF ROUGH FORMS 



Tillett 1406 turned his attention to the antigenic properties of the 

 dissociated R forms. When he vaccinated rabbits by repeated in- 

 travenous injections of suspensions of heat-killed R pneumococci, 

 the animals acquired a marked degree of active immunity to infec- 

 tion with virulent S forms of Pneumococcus I and II. (Tillett 14046 

 had previously shown that a similar immunization treatment in- 

 duced active resistance to Type III infection.) Furthermore, the 

 whole citrated blood of the immune rabbits passively protected 

 normal rabbits against infection with Type I and Type III pneu- 

 mococci, but failed to confer a like protection on mice. According 

 to Tillett this form of acquired resistance to pneumococcal infec- 

 tion elicited by R organisms devoid of type-specificity, and exem- 

 plified in animals whose serum possessed no demonstrable type- 

 specific antibodies, presented features which strongly suggested 

 that the underlying mechanism differed from that concerned in 

 type-specific immunity.* 



RESPIRATORY CAPACITY OF VARIANTS 



Another difference in the character of S and R forms was the 



* For a full discussion and bibliography of microbic dissociation up to that 

 time the reader is referred to Hadley's^ comprehensive article. 



