CULTIVATION OF PNEUMOBACILLUS 239 



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 Schottmuller, 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 differs 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 

 agglutinate the streptococcus mucosus more readily than other 

 streptococci. All the facts seem to point to this organism being 

 closely allied to the true pneumococcus. 



The Cultivation of Friedlander's Pneumobacillus, This 

 organism, when present in sputum or in a pneumonic lung, can 

 be readily separated by making ordinary gelatin plate cultures, 

 or a series of successive strokes on agar tubes. The surface 

 colonies always appear as white discs which become raised from 

 the surface so as to resemble little knobs of ivory. From these, 

 pure cultures can be readily obtained. The appearance of a stab 

 culture in gelatin is sometimes very characteristic. At the site 

 of the puncture, there is on the surface a white growth heaped 

 up, it may be fully one-eighth of an inch, above the level of the 

 gelatin ; along the needle track there is a white granular appear- 

 ance, so that the whole resembles a white round-headed nail 

 driven into the gelatin (Fig. 67). Hence the name " nail-like " 



