PATHOGENIC BACTERIA. 249 



arranged in pairs or in fours; about i fJ- in diameter; not 

 motile; stain by Gram's method. It grows well at the room 

 temperature, but rather slowly; is a facultative anaerobe; 

 does not liquefy gelatin. Gelatin plates show httle, white, 

 punctiform colonies, which, with the low power, are finely 

 granular, and have a peculiar glassy shimmer; in stab-cultures 

 the growths appear as little colonies along the line of puncture. 

 On agar, round white colonies form, which do not tend to 

 spread. It produces a thick, slimy film on potato and a broad, 

 white, moist growth on blood-serum. This organism is only 

 occasionally found in pus. It is pathogenic for white mice and 

 guinea-pigs, but not for gray mice and rabbits. It may produce 

 septicemia or only a localized suppuration in guinea-pigs. In 

 white mice general septicemia results on inoculation and the 

 Micrococcus tetragenus is found in the blood and in the great 

 viscera. White mice usually die in from two to six days ; guinea- 

 pigs in from four to eight days from inoculations. 



Micrococcus lanceolatus (Micrococcus pneumoniae crou- 

 posae; Micrococcus Pasteuri; Diplococcus pneumonia:; Micro- 

 coccus of Sputum Septicemia; Streptococcus lanceolatus Pas- 

 teuri; and Pneumococcus of Frankel). — ^This organism was 

 discovered by Sternberg in his saliva in 1880, and afterward 

 demonstrated to be the cause of lobar pneumonia by Frankel 

 and Weichselbaum. The micrococci usually occur in pairs. 

 The pair of micrococci, in its most typical form, appears like 

 a couple of curved triangles with their bases close to each 

 other. The outline is usually described as being lancet-shaped. 

 The micrococci are frequently oval or round; they often form 

 chains. In preparations made from the blood of infected ani- 

 mals or from pneumonic sputum each pair of micrococci is seen 

 in stained preparations to be surrounded by a capsule; the 

 capsule is not usually seen in preparations made from cultures. 

 For methods of demonstrating the capsule see pages 45 and 46. 

 The pneumococcus is not motile. It stains by Gram's method. 



