56 BIOLOGY OF PNEUMOCOCCUS 



by Levy, 803 were denied by Mandelbaum, 865 who maintained that 

 while the former dissolved strains of Pneumococcus and Strepto- 

 coccus mucosus as against a negative action on other streptococci, 

 dissolution was not so complete as that produced by bile. The par- 

 tial failure of sodium taurocholate may have been due, as pointed 

 out by Levy, to lack of uniformity in commercial preparations of 

 the salt. A pure preparation of this bile-salt is to be preferred to 

 whole bile, because solutions of constant concentration may be 

 prepared, sterilized, and kept in stock for quantitative or repeated 

 tests. 



Malone 861 would further refine the test by always using the same 

 strength of sodium taurocholate (10 per cent), keeping the den- 

 sity of the bacterial suspension uniform, employing cultures from 

 solid rather than from liquid media, holding both time and tem- 

 perature constant, and taking precautions that the mixtures are 

 always alkaline in reaction. For routine identification tests such 

 refinements seem to be superfluous. 



Neufeld at first held the view that only freshly isolated and viru- 

 lent strains of pneumococci were susceptible to the solvent action 

 of bile, but Levy, 833 using sodium taurocholate in a 5 to 10 per 

 cent solution, believed that the method afforded a clear-cut differ- 

 entiation between all pneumococci and streptococci and other bac- 

 terial species. It was Levy who, in 1907, with this confirmatory 

 test, definitely established Streptococcus mucosus as a pneumo- 

 coccus, and called it Pneumococcus mucosus. 



Neufeld's view concerning the correlation between virulence and 

 bile-solubility was upheld by Truche, Cotoni, and Raphael 1425 who, 

 after an experience of several years, reported that high virulence 

 always accompanied complete solubility and total avirulence went 

 with insolubility, whereas strains of slight virulence showed partial 

 or varying solubility. All thirty-one strains of streptococci tested 

 were insoluble in bile. Malone 861 " 2 also observed that pathogenic 

 strains and members of fixed types tended to fall into a sodium 

 taurocholate soluble group, while the so-called "normal" strains 



