154 BIOLOGY OF PNEUMOCOCCUS 



globin in blood. Without an actual visual comparison of these V 

 variants with the principals and intermediates described by other 

 authors it is impossible to assign them their proper place in the 

 dissociation order. 



Further study is required before giving an estimate of the sig- 

 nificance of these possibly new forms, although there is already 

 much evidence to support the concept of a polyphasic cycle in bac- 

 terial dissociation.* 



REVERSAL OF DISSOCIATION 



Griffith 562 was successful in reversion experiments in the animal 

 body. Some R strains which had not entirely lost their soluble spe- 

 cific substance readily reverted to the S form when passed through 

 the mouse. The author obtained smooth colonies, with restoration 

 of virulence and original serological type characters, after making 

 massive injections of R strains into the subcutaneous tissues of the 

 mouse. The original change from S to R forms was accomplished 

 by ageing the colonies on chocolate blood agar containing horse 

 serum and by cultivation in broth to which specific immune serum 

 had been added. The greater the concentration of immune serum, 

 the more complete and permanent was the change to the R form. 



The possibility of the reversal of the dissociation process at- 

 tracted Dawson and Avery 304 who, by mouse passage, not only 

 brought back to the S form seven or eight cultures of single-cell 

 isolation, pure-line S strains of Types I, II, and III, but also suc- 

 ceeded in causing six pure-line R strains to revert to type-specific 

 forms by growing the cultures in media containing anti-R serum. f 

 The authors failed in a similar attempt with a Type IR culture. As 

 in mouse passage, reversion by cultural methods was accompanied 



* Rakietenins believed that a peculiar organism obtained from the peritoneal 

 fluid and heart's blood of a mouse after inoculation with a highly virulent Type 

 II Pneumococcus was a pneumococcal variant. It was a Gram-positive bacillus, 

 bile-soluble, agglutinated with Type II serum in a dilution of 1 to 400, and also 

 to a slight extent with Type I serum. The organism was not pathogenic for 

 mice. Rakieten's description of cultural development of the strain from the in- 

 fected fluids raises doubt as to its true pneumococcal origin. 



f Compare Soule'sisos similar results with Bacillus subtilis (1927). 



