140 THE CYTOLOGY AND LIFE-HISTORY 



BACTERIA 



Bacteria of rough morphology vary considerably in rigidity between 

 such extremes as Bacillus mycoidcs, which is so rigid that it seldom produces 

 any structure more complex than a primary coil, and grows out, as long 

 threads across the agar, and, upon the other hand those rough Bacteriacecv 

 whose colonies are almost indistinguishable from smooth variants. 



Rough colonies are not confined to the surface of artificial culture medium. 

 They may torm wherever a flat surface is presented to growth, provided that 

 the substrate is not too fluid. 



The structure of these colonics may be entirely disguised by the production 

 of mucoid capsular material. The anthrax bacillus may produce its polypeptide 

 capsule under suitable cultural conditions, o( which COo tension is one of the 

 most important. The phenomenon of smooth-trough variation in pneu- 

 mococci is entirely concerned with the production or loss of polysaccharide 

 capsular material, concealing or revealing the rough appearance ot the colony 

 (Section G). 



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v^r^: 



{Ri-proclucitl fiiim the Joiinuil af Pathology and Bacteriology.) 



A B 



Fig. 62 

 SMOOTH AND ROUGH COLONIES 



A. Smooth colony, Bact. coli, impression preparation x 500. 



H. RouKh colony arising from the perimeter of a smooth colony, Shigella flcxneri, 



■ .sod. ■ ' ' 



