SHERWOOD: PLEOMORPHIC STREPTOCOCCI. 249 



cell isolation. The individual organisms were inoculated into the 

 moisture of condensation of agar slants, and after several hours 

 the water was permitted to cover the surface of the slant. In this 

 way growth was obtained. The author was unable to get very- 

 large individual coccus forms to grow satisfactorily, although Dr. 

 F. Hecker has privately reported success. The resulting cultures 

 from the above isolations showed as marked pleomorphic varia- 

 tions as the other cultures. As a rule, successive transfers in 

 dextrose broth would yield uniform chains in time, but involution 

 forms reappeared when transfers were made to solid media, espe- 

 cially if partially desiccated media were used. Very frequently 

 beautiful chains could be obtained from the deeper part of the 

 stab in Russell's medium when the stab was made next to the 

 glass, while involution forms predominated upon the surface of 

 the slant. 



The Streptococcus pyogenes, and in fact the rest of the strepto- 

 coccus group, is usually described as chains of cocci of compara- 

 tively uniform size, but varying in length of chain, pathogenicity, 

 action on litmus milk, various carbohydrates, glucosides and 

 neutral red. 



IMuch work has been done which suggests that perhaps there 

 are not so many different streptococci as has been generally thought, 

 but that one or at most a few organisms make up the group and 

 that these are very plastic and subject to much variation. Heine- 

 man^" and others have concluded that Streptococcus pyogenes and 

 Streptococcus lacticus are perhaps one and the same. Rosenow". 

 has reported remarkably induced mutations in streptococci. He 

 has converted hemolytic streptococci from many sources, such as 

 erysipelas, scarlet fever, puerperal fever, arthritis, tonsillitis, milk, 

 etc., into Streptococcus viridans, Streptococcus mucosus, and typical 

 pseudopneumococci; Streptococcus viridans into Streptococcus mu- 

 cosus, Streptococcus hemolyticus and Streptococcus rheumaticus; 

 Streptococcus mucosus into Streptococcus viridans and Streptococcus 

 hemolyticus; Streptococcus rheumaticus into Streptococcus viridans 

 and pneumococci. In this work he made use of pure cultures iso- 

 lated by Barber's pipette method for single cell isolation: Billings 

 and Rosenow^- record quite a remarkable observation of bacterial 

 mutation from a bacillus to a coccus form. They report colonies 

 on dextrose agar showing only bacillus forms yielded in sub- 

 culture; a staphlococcus in pure cultures; and forms of the bacillus, 

 either pure or in a mixture, anerobically on the same media. 



