THE REVERSION OF R TO S PNEUMOCOCCI.

A study was made of the behavior of R pneumococcus strains under various experimental conditions. It was found that daughter colonies frequently appeared among the R forms and in some instances tended to replace the typical R forms. The daughter strain produced colonies with shiny surfaces which were morphologically indistinguishable from genuine S colonies although the characteristics of the bacteria comprising them conformed to the R variety. Both R and daughter forms which had resided for long periods of time in vivo have been converted into virulent forms. Strains of R pneumococci which seemed irreversible were apparently converted into S forms by applying the methods of Griffith. A general consideration of the information derived during the recent experimental studies indicates that virulent S pneumococci may dissociate into the R form in vivo, that the R forms may be occasionally found in the sputum of pneumonia patients and also may reside or lie dormant in vivo for a considerable period of time. It has been shown that under favorable circumstances bacteria of the R form may spontaneously revert to the original S form or by special methods may even transform into S forms of another type.