162 BIOLOGY OF PNEUMOCOCCUS 



and continuous. In the first stage, which may suitably be termed R 1 , the 

 colonies present more or less the general appearance of smooth (old ter- 

 minology, "rough") colonies but the surface is more coarsely stippled. 

 The constituent organisms are more or less typical pneumococci show- 

 ing a tendency to staphylococcal grouping and occasional swollen or 

 club forms may be seen. In the second stage, R 2 , the colonies present a 

 still rougher appearance and the outline may appear slightly irregular. 

 This irregularity frequently becomes quite pronounced after several 

 days' growth. The bacteria in this stage are much more pleomorphic 

 and are frequently elongated in an extreme lanceolate manner. They 

 still retain Gram's stain. In the third stage, R 3 , the surface of the col- 

 ony becomes exceedingly rough and the margin quite irregular. The 

 contour of such colonies still remains convex but less so than the origi- 

 nal S form (old terminology, R form). The organisms constituting such 

 colonies present a bizarre morphological picture. Pointed diphtheroid 

 elements arranged in a fashion suggesting broken twigs may be ob- 

 served, with scattered long, bizarre, rod forms which are partially 

 Gram-positive and partially Gram-negative. At this stage of develop- 

 ment the morphological picture can scarcely be recognized as that of 

 pneumococcus. The fourth stage, R 4 , can only be defined with some 

 difficulty. It would appear that the growth is now in a stage of con- 

 siderable flux and several types of colonies and morphological elements 

 may be produced. Some of the colonies present an appearance similar to 

 that just described while others resemble more closely the pure R form 

 (R»). 



The morphology of the organisms in the R 4 stage is difficult to de- 

 scribe because of their extreme pleomorphism. In addition to coarse and 

 irregular coccal forms there may appear elongated Gram-negative rod- 

 like structures exhibiting irregular Gram-positive areas. A great va- 

 riety of other morphological elements may also be present. 



Dawson described the R — » S change in which intermediate forms 

 of the type seen in the S — > R change were not observed, and then 

 gave a detailed description of the biological characters of this new 

 variant. From the description a few of the more important data 

 may be selected. The organism was bile-soluble, of low virulence for 

 mice, agglutinated in normal saline solution, and failed to elabo- 

 rate soluble specific substance. The variant was not peculiar to the 



