136 BIOLOGY OF PNEUMOCOCCUS 



nently modified pneumococci, Streptococcus mucosus, or strepto- 

 cocci of hitherto unrecognized types. 



A suggestive communication, because of its anticipation of later 

 discoveries, was that of Rosenow 1163 published in 1910. He pre- 

 sented the results of a study of seven cultures isolated from endo- 

 carditis which he believed were "modified pneumococci." All the 

 strains fermented inulin and produced a variable amount of green- 

 ish discoloration but no hemolysis on blood-agar plates, but grew 

 atypically with the development of involution forms on media con- 

 taining the patient's blood. However, cultivation in normal serum 

 or blood and animal passage promptly restored normal pneumo- 

 coccal characters to the modified strains. Recultivation in the pa- 

 tients' serum brought out the modified characters. These special 

 characters varied greatly in the strains studied ; the more chronic 

 the disease process in the patient from whom the serum was ob- 

 tained, the more marked were the changes. This last observation 

 would seem to argue for the occurrence of variation or dissociation 

 in vivo — a biological process concerning which there is still some 

 doubt. 



The phenomenon of bacterial dissociation, or as it was known 

 in the early years of this century, variation, received little atten- 

 tion until 1915 when Friel 494 reported that prolonged cultivation 

 of bacteria rendered them more susceptible to phagocytosis. He 

 called the process "Piantication" (fattening for slaughter) and 

 observed its operation with strains of Friedlander's bacillus, Pas- 

 teurella, and Pneumococcus. The same effect was produced by ex- 

 posing the organisms to immune serum ; while the reverse process 

 took place when "pianticated" bacteria were grown in normal se- 

 rum — they regained their resistance to phagocytosis.* 



In the next year, Stryker 1348 described the variations induced in 



* Neufeld and Schnitzer credited the first demonstration of bacterial dis- 

 sociation to Friel, although Hadleyss* ascribed the discovery to Baerthlein 

 (1912). The phenomenon had, however, been observed much earlier by Kruse 

 and Pansini (1891),763 and by Arkharow (1892),i7 and had been described in 

 some detail by Eyre and Washbourn373 in 1897. 



