152 BIOLOGY OF PNEUMOCOCCUS 



respiratory functions and to maintain their reproductive capaci- 

 ties and virulence for a longer period of time. 



Petrie (1932) 1084 suggested one more means for the identifica- 

 tion of R and S variants. In stab cultures in agar plates contain- 

 ing 5 per cent immune serum the virulent S pneumococci grew with 

 a distinct halo about the colony when the organism and immune 

 serum corresponded in type-specificity. The halo apparently con- 

 sisted of a specific precipitate formed by the interaction of the 

 pneumococcal polysaccharide and the precipitin in the homolo- 

 gous serum. The R colonies, in contrast, produced only a faint and 

 narrow halo after a considerable period of incubation. Serum from 

 immune horses appeared to be more suitable than serum from im- 

 mune rabbits for halo production. 



INTERMEDIATE FORMS 



In addition to the well-known S and R forms, Klumpen (1932) T80 

 mentioned intermediate forms growing in colonies designated as 

 SU and RK. In other characters, however, the strains were either 

 true S or R forms. Klumpen recognized the Flatterformen de- 

 scribed by Grumbach, and noted that the organisms comprising 

 daughter colonies were of the smooth type. 



Still other variants intermediate between the S and R forms 

 were derived from pneumococci by Blake and Trask (1933). 130 By 

 growing Type IS pneumococci in homologous immune serum broth, 

 the progressive appearance and disappearance of forms differing 

 from both S and R cocci were observed. The forms were desig- 

 nated as a, b, c, d, and e. Two of the intermediates, Type lb and 

 Type Ic, were easily stabilized in pure culture. All showed an or- 

 derly change in agglutinative reactions in homologous and heter- 

 ologous immune serum, and also underwent a progressive loss of 

 virulence for mice. Blake and Trask produced only one intermedi- 

 ate form from Type IIS and none from Type HIS. 



The importance of recognizing intermediate variants in the dis- 

 sociative process was emphasized by Paul 1069 of Blake's labora- 



