370 PATHOGENIC MICROORGANISMS 



Cultivated on whole-blood-agar, streptococci usually cause hemo- 

 lysis, pneumococci usually do not. 1 In contradistinction to Streptococ- 

 cus viridans which does not hemolyze, pneumococci have a tendency on 

 these media to form the black, dry, paint-blister colonies. 2 



Neufeld, 3 in 1900, noticed that normal rabbits' bile added in quan- 

 tities of 0.1 c.c. to each one or two cubic centimeters of a pneumococcus 

 broth culture caused lysis of the bacteria, rendering the culture fluid 

 transparent and clear. This does not occur with streptococci, and has 

 been used to differentiate the two species. According to Libman and 

 Rosenthal, 4 great reliance may be placed upon this method. 



The most convenient reagent for use in the Neufeld bile test is a 

 10 per cent solution of sodium taurocholate in physiological salt solution. 

 This should be sterilized or kept on ice. One-tenth volume of such a 

 solution produces prompt lysis in a broth culture of pneumococci. 



Decisive differential importance may be attached to the agglutina- 

 tions of these microorganisms in immune sera (see p. 364). . 



The permanency of the various types in the pneumococcus-strepto- 

 coccus group is still open to question. E. C. Rosenow 5 has recently re- 

 ported that he has transmuted typical pneumococci into typical hemo- 

 lytic streptococci by methods which he has not as yet fully described, but 

 among which were animal passage, growth in symbiosis with bacillus 

 subtilis, and growth in an atmosphere of oxygen. The pneumococci 

 when first altered took on the characteristics of the streptococcus 

 viridans, later of the so-called streptococcus rheumaticus, and finally 

 of streptococcus hemolyticus. Together with cultural characteristics 

 the pathogenicity of these various strains for rabbits changed. The 

 pneumococcus produced acute sepsis, the streptococcus viridans caused 

 endocarditis, the streptococcus rheumaticus periarticular or serous 

 arthritis, and hemolyticus suppurative arthritis. In intermediate stage 

 the organisms quite regularly caused myositis. Although he was able 

 to transmute these types one into the other in both directions, Rose- 

 now believes that the cultural characteristics of each type correspond 

 to a fairly definite type of pathogenicity in animals and man. This 

 work has not as yet appeared in detail and has not been confirmed. 



1 Schottmuller, Miinch. raed. Woch. 



2 Hiss, Jour. Exp. Med., vii, 1905. 

 Neufeld, Zeit. f. Hyg., 1901. 



4 Libman and Rosenthal, Proc. N. Y. Path. Soc., March, 1908. 

 1 Rosenow, J. A. M. A., 1913, Ixi, 2007. 



