BIOLOGY OF PNEUMOCOCCUS 57 



and cocci of Group IV fell into either soluble or insoluble groups, 

 with some strains intermediate between the two. 



Schiemann's* observations did not agree with those of Neufeld. 

 He found completely avirulent strains which were still bile-soluble, 

 as well as mouse-virulent strains which were insoluble. Cocci in the 

 blood and peritoneal exudate of freshly dead mice resisted dissolu- 

 tion, while transitional forms were only incompletely dissolved. 

 Cotoni* described some virulent, typical pneumococci as insolu- 

 ble. In marked contrast to these results were those of Falk and 

 Jacobson 381 who could find no relation between virulence and bile- 

 solubility, since avirulent strains appeared to be as sensitive to the 

 lytic action of bile as were virulent cultures. Kelly, 702 too, noted a 

 variation in the susceptibility of different strains to lysis, but 

 added that specimens of bile differed in solvent power, and that the 

 presence of sugar in the medium containing the pneumococci had 

 an inhibitory action on the lytic action of bile. Human blood se- 

 rum, on the contrary, according to Ziegler, 1570 does not interfere 

 with this power. 



Differing in their experience from that of Neufeld, Cole and his 

 colleagues 36 found all of several hundred strains of Pneumococcus 

 isolated from lobar pneumonia to be bile-soluble. There are rare 

 exceptions to this rule, an example being the strain of Pneumococ- 

 cus mucosus reported by Dochez and Gillespie. 322 It seems safe to 

 say, with Mair, 552 that "different strains of Pneumococcus show 

 varying sensitiveness to the action of bile, just as they vary in the 

 readiness with which they undergo autolysis in culture, but with a 

 satisfactory technique one is very seldom in doubt as to whether a 

 particular strain should be classed as bile-soluble or not, and 

 strains which have been kept on culture media for long periods re- 

 tain the property ."f 



* Quoted by Neufeld and Schnitzer. 



f Sellardsi25* also stressed the importance of the characters of the cultures 

 and the alkalinity of the medium in solubility tests. In place of bile Sellards 

 substituted 0.01 N to 0.2N solutions of sodium hydroxide, which even in the 

 stronger concentration failed to dissolve streptococci. He thought that old 

 strains of pneumococci were more soluble than young strains. 



