CULTIVATION OF PNEUMOCOCCUS 231 



organism be grown in rabbit or human serum which has been 

 obtained under aseptic precautions and heated for half an hour 

 at 55 C. 



The pneuinococcus ferments saccharose, raffinose, and lactose, 

 and a similar fermentative action on inuliri is important, as 

 ordinary streptococci do not so readily ferment this sugar. 

 Apparently some samples of inulin are more readily acted on 

 than others. Usually the test is carried out with Hiss's inulin 

 serum water medium, in which coagulation of the serum results 

 (p. 47), but some investigators have had more success with 

 inulin bouillon, acid production being estimated by titration 

 against soda with a phenolphthalein indicator. 



There has been described by Eyre and Washbourn a non- 

 pathogenic type of the pneumococcus which may be found in 

 the healthy mouth, and which may also be produced during the 

 saprophytic growth of the virulent form. From the latter it 

 differs generally in its more vigorous growth, in producing a 

 uniform cloud in bouillon, in slowly liquefying gelatin, and in 

 growing on potato. The facts that in cultures the pneumococcus 

 often grows in chains, and that occasionally streptococci are 

 found to develop capsules, have raised the question of the rela- 

 tionship of the pneumococcus to other streptococci. When, 

 however, biological characters are taken along with morpho- 

 logical, relatively little difficulty arises in the recognition of a 

 true pneumococcus. Here the reaction in inulin is important. 

 It may be said that the capacity of a capsulated organism to 

 produce acid from this sugar makes its being a true pneumococcus 

 extremely probable. That the pneumococcus may be related to 

 other streptococci is, however, shown by the fact that both sets 

 of organisms tend to originate common group agglutinins. 



Considerable attention has been devoted to a bacterium 

 originally described by Schottmiiller, and called by him the 

 Streptococcus mucosus. This organism has been isolated from 

 a variety of suppurative conditions and also from certain cases of 

 pneumonia. In culture, it diners from the pneumococcus in the 

 colonies being more clear, transparent, and dewdrop-like, showing 

 great tendency to confluence, and being more slimy than those 

 of the pneumococcus. It coagulates the serum in Hiss's inulin 

 serum water medium. It is, pathogenic to white mice, but its 

 pathogenicity in the rabbit seems to be less than that of the true 

 pneumococcus. Its agglutinative reactions are somewhat pecu- 

 liar. Unlike the pneumococcus, it produces in animals only a 

 weak agglutinating serum, but such a serum often can agglu- 

 tinate pneumococci. Further, antipneumococcal sera frequently 



