DISSOCIATION AND TRANSFORMATION 177 



Finally single cell cultures originating in their time from a single cell 

 of a pneumococcus have been examined with regard to the degree of 

 dissimilarity which such cultures can eventually show. These experi- 

 ments gave the result that two pneumococcus cultures, obtained from 

 the same cell, can show much greater dissimilarities than two cultures 

 obtained one from a typical Streptococcus viridans and the other from a 

 typical Streptococcus lanceolatus. . . . Thus Streptococcus viridans 

 and Pneumococcus lanceolatus seem to be different forms of the same 

 bacterium, and the specific agglutinability, which Pneumococcus lan- 

 ceolatus shows when grown from the human body and which has been 

 taken as a base for the so-called type classification, is only an occa- 

 sional character. 



Summary 



Virulent pneumococci of all the known serological types, upon 

 encountering unfavorable physical, nutritional, or other biochemi- 

 cal conditions during growth or storage, undergo marked changes 

 in virulence, in ability to elaborate capsules, in colony develop- 

 ment, and in their immunological characters. In studies on the dis- 

 sociation phenomena displayed by pneumococci, a great variety 

 of aberrant coccal forms have been observed which are intermedi- 

 ate between the typical, virulent form and the thoroughly de- 

 graded, atypical form. So many variants with such a diversity of 

 biological characters have been described and so many designa- 

 tions have been given to the intermediate forms, that it is difficult 

 to gain a clear conception of the significance of the many phases 

 of pneumococcal dissociation. In order to bring order out of this 

 chaos and to make the nomenclature applied to pneumococci uni- 

 form with that employed in naming the variants occurring in the 

 case of other bacterial species, it has been proposed to change the 

 terminology now in use. Mucoid or M would replace the present 

 smooth or S ; smooth would be substituted for. rough ; while rough 

 or R would apply to a recently discovered variant. Whatever the 

 fate of the proposal, the alterations in character which may be 

 induced in pneumococci by appropriate means constitute one of 

 the most important features in the biology of the species. 



