DISSOCIATION AND TRANSFORMATION 



163 



Type IIR strain, and single organisms of one individual strain 

 also possessed the capacity to dissociate into the new form. 



Dawson then pointed out certain discrepancies in the character- 

 istic features of the S and R forms as described by Griffith for 

 Pneumococcus and those described by Arkwright for the colon- 

 typhoid-dysentery group, and which have been accepted by the 

 majority of bacteriologists as the chief distinguishing features of 

 the smooth and rough forms of many bacterial species. He fur- 

 ther drew attention to the fact that certain attributes of Ark- 

 wright's S and R forms do not appear in Pneumococcus while 

 other new distinctions did not have a place in Arkwright's original 

 descriptions. Dawson has portrayed these differences in termi- 

 nology in a diagram which, although as yet unpublished, was 

 kindly loaned to the authors. 



Courtesy of Dr. M. A . Dawson 



RELATIONSHIPS OF MUCOID, SMOOTH, AND ROUGH COLONIES 



OF BACILLI OF THE COLON-TYPHOID-DYSENTERY 



GROUP AND PNEUMOCOCCUS 



