168 BIOLOGY OF PNEUMOCOCCUS 



unfavorable conditions continue, this particular metabolic activity 

 ceases or is suppressed and the organism degenerates into a harm- 

 less coccus, devoid of any specialized earmarks — a sort of bac- 

 terial maverick. If the exposure to these untoward conditions is 

 sufficiently protracted, the function is apparently permanently 

 lost, but if the exposure ceases before this stage is reached, the 

 cell retains the latent power to elaborate its original, individual 

 capsular carbohydrate, and all that is needed to revive this power 

 is the restoration of a satisfactory environment — either in culture 

 or in an animal — or else the activation that comes from an encoun- 

 ter with immune bodies specific for its own degraded form. Living 

 under such conditions the type-less coccus gradually returns to its 

 former distinctive state. 



These discoveries, moreover, have disclosed another and aston- 

 ishing activity of the organism. When stimulated by some un- 

 known constituent of fully functioning pneumococcal cells, this 

 latent metabolic function of the degenerated coccus develops a new 

 property, and instead of building up capsular carbohydrates of 

 the former kind, the degraded cell now synthesizes polysaccharides 

 of the same chemical constitution and specific type as those of the 

 strains supplying the activating stimulus. The once degraded or- 

 ganism becomes then a virulent pneumococcus, but with all the spe- 

 cialized characters of its foster strain. Having lost its original 

 features it regains a new type identity. 



The cycle of degradation, regeneration, and type transforma- 

 tion presents so many fascinating phases that one is strongly 

 tempted to speculate on the various factors concerned in this ex- 

 traordinary evolution. The basic ability to elaborate these various 

 specific capsular carbohydrates is always ready to respond to ap- 

 propriate stimulation unless the cells have gone too far down the 

 path of degradation, and is evidently common to all pneumococci. 

 The direction which the transformation takes is determined wholly 

 by the nature of the stimulus, and it is the identity of this factor 

 which still remains unrevealed to us. It apparently exists only in 



