THE GENUS DIPLOCOCCUS 121 



great numbers; but they all appear to group themselves 

 about a single type, and this type may be defined as 

 follows : 



i. D. PNEUMONIA (Weichselbaum). A coccus occur- 

 ring commonly in the body, in pairs of elongated lanceolate 

 cells, surrounded by a capsule. Stains by Gram. On 

 media often in short chains. Growth on media faint, 

 producing small translucent disk-like surface colonies. 

 Ferments monosaccharides, disaccharides, and inulin. 

 Lacks hemolytic power. Virulence very variable. Shows 

 characteristic group serum reactions. Occurs in normal or 

 pneumonic sputum and in infected tissues in pneumonia. 



Whether pneumonic infections of horses and cattle are 

 due to specific organisms allied to D. pneumonia is not 

 yet certain. The descriptions of the various forms 

 isolated from such sources are so imperfect that it is even 

 uncertain whether they are cocci or bacilli. 



Two other pathogenic diplococci, D. Weichselbaumii 

 and D. gonorrhcece, clearly belong to this genus; and 

 they and their varietal strains form a well-marked series, 

 distinguished from D. pneumonia and its allies by mor- 

 phological and cultural relations. Both organisms 

 occur in pairs of flattened cells instead of lance-shaped 

 ones. Both are Gram-negative, and both grow much 

 less readily on artificial media than does D. pneumonia. 

 D. gonorrhoea (Neisser, Fliigge), was discovered by 

 Neisser (1879) and was known as the Gonococcus until 

 given a specific name by Fliigge (1886). It was first 



