PNEUMOCOCCUS 165 



with human saliva. They did not, however, associate the organism 

 they saw with lobar pneumonia. Later, in 1886, Frankel and 

 Weichselbaum demonstrated beyond question that the large 

 majority of the cases of lobar pneumonia are caused by the pneu- 

 mococcus. 



Morphology and Staining. Ordinarily the organism appears 

 as a small, slightly oval coccus, one side of which is somewhat 

 pointed. The pneumococci may occur singly or in chains, and 

 for this reason they are classed by certain authorities with the 

 streptococci; usually they appear in pairs with the broad ends 

 of the oval in juxtaposition and the pointed ends turned outward. 

 When observed in fresh sputum or blood smears they are sur- 

 rounded by a well-defined capsule. Cultivated on artificial 

 media the capsule is rarely seen unless serum or blood has been 

 incorporated in the medium. The organisms are non-motile, 

 possess no flagella, and do not form spores. They stain readily 

 with the ordinary dyes and are Gram positive. The capsule 

 may be easily demonstrated in blood or sputum preparations by 

 the method already described. 



Cultivation. The temperature range of the pneumococcus is 

 rather limited, growth taking place as a rule only between 22 C. 

 and 42 C. It grows equally with or without oxygen. When 

 freshly isolated, growth is very feeble unless blood or serum is 

 added to the medium; on agar or gelatin the colonies appear 

 similar to those of the pyogenic cocci except that they are more 

 delicate in appearance. The same may be said of stab cultures 

 in gelatin. Along the line of inoculation a row of minute points 

 appear which remain of a small size ; there is no liquefaction of 

 the medium. In broth a slight turbidity is produced which 

 settles to the bottom of the tube as a fine deposit. Milk is quickly 

 acidified and often but not always coagulated ; growth on potato 

 is seldom visible. 



The pneumococcus is non-hemolytic ; its colonies on blood 

 agar are of a greenish color. Glucose, saccharose, lactose, and 

 inulin are fermented ; the ability to ferment the latter sugar and 

 the fact that the organisms are dissolved in bile are two important 



