164 BIOLOGY OF PNEUMOCOCCUS 



When Dawson compared the salient characters of the three 

 pneumococcal variants (S, R, and the new M form) with the mu- 

 coid, smooth, and rough forms of members of the colon-typhoid- 

 dysentery group and the smooth and the two rough forms of the 

 Friedlander bacillus, the inconsistency in the use of the terms 

 smooth and rough became convincingly apparent. On a basis of 

 colony appearance, morphology, growth in plain broth, stability 

 in salt solution, and of virulence and type-specificity, the smooth 

 form of Pneumococcus and of Friedlander's bacillus conforms to 

 the mucoid form of members of the colon-typhoid-dysentery group ; 

 the rough form of Pneumococcus and the R x form of Friedlander 

 are similar to the smooth form of bacilli of the enteric group ; while 

 Dawson's new variant and Julianelle's R 2 form of the Friedlander 

 bacillus agree with the rough form of the colon-typhoid-dysentery 

 bacilli. 



In order, therefore, to bring these terms in agreement, to con- 

 form — with an addition — to the designations of Arkwright, and to 

 establish a uniform and logical terminology for the dissociants of 

 all bacterial species, Dawson would change the terms now used for 

 the variants of pneumococci as follows: Mucoid or M would re- 

 place the present smooth or S ; smooth would be substituted for the 

 former rough (R x form of Friedlander bacilli) ; while rough or R 

 would be applied to the new variant described by Dawson and the 

 R 2 form of Friedlander's bacillus. 



There is no doubt that such a reversal of the accepted terms 

 would cause confusion and meet with opposition. It cannot be de- 

 nied that this change would be especially disturbing to the present 

 correlation between the classification of dissociation forms and 

 immunological behavior, but that does not necessarily preclude the 

 possibility of a new and perhaps a deeper insight into the parallel- 

 ism between the phenomena of variation and antigenic specificity. 

 This proposed change recalls the confusion that followed the revi- 

 sion of the designations of blood groups, but that change has not 

 only been endured but the new terms are now generally accepted as 



