138 BIOLOGY OF PNEUMOCOCCUS 



type, are virulent for laboratory animals, and on injection into 

 rabbits stimulate the production of type-specific immune sub- 

 stances. The R colonies have a rough surface, and the organisms 

 comprising them form no soluble specific substance in broth cul- 

 ture, agglutinate atypically, and are avirulent. Cocci of the R 

 colonies may revert to the S form, or they may remain stable for 

 generations. Another property of the S cells is the ability to ab- 

 sorb from immune serum all antibodies for both S and R forms. 

 The R forms absorb only the anti-R bodies, and when injected into 

 animals fail to stimulate the formation of type-specific (S) anti- 

 bodies. 



Griffith considered that the R form was differentiated from the 

 S by the loss of virulence and by the ability to form capsules and 

 to elaborate soluble specific substance, and that the R form repre- 

 sented a stage in the degeneration of Pneumococcus from the viru- 

 lent, complex type of S cell to an attenuated form with a simpler 

 antigenic structure. Griffith also found that degradation might not 

 be permanent and that reversion could take place after animal pas- 

 sage or repeated cultivation in blood broth. The author recom- 

 mended for the demonstration of variant colonies an opaque 

 "chocolate" agar to which red blood cells treated with chloroform 

 had been added. 



Griffith looked upon the S form as the original, unchanged or- 

 ganism, the R form as a variant due to unusual growth conditions. 

 The degenerative action of immune serum Griffith believed to be a 

 double one. He suggested as an explanation of the change the view 

 that serum might disorganize the biological functions of Pneumo- 

 coccus by precipitating the capsule, thus inhibiting the secretion 

 of antileucocytic substances and rendering the organism tempo- 

 rarily harmless, and that when pneumococci divided in the animal 

 body in the presence of immune serum, the influence of the serum 

 might cause progressive attenuation of subsequent generations. In 

 connection with the causes for such bacterial variations, East- 

 wood 344 contributed an interesting theoretical discussion. It would 



