PATHOGENIC BACTERIA. 



301 



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

 guinea-pigs in from four to eight days from inoculations. 



Micrococcus Lanceolatus (IMicrococcus pneumonije crou- 

 posse; Micrococcus Pasteuri; Diplococcus pneumoniae; 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 animals or 

 from pneumonic sputum each pair of micrococci is often seen 

 in stained preparations to be surrounded by a capsule; though 

 even in such preparations the capsule is sometimes difficult 

 to demonstrate; the capsule is not usually seen in preparations 

 made from cultures. For methods of demonstrating the 

 capsule see pages 49 and 121. The penumococcus is not motile. 

 It stains by Gram's method. It grows on potato, but the 

 growth is not visible to the naked eye* 



As with most other pathogenic bacteria, the indentification 

 of the pneumococcus is uncertain from observation of its 

 morphology and staining properties alone. These have to be 

 supplemented as in other cases by cultures and animal 

 experiments. 



It is facultatively anaerobic. It grows only at elevated 

 temperatures, preferably about 35° to 37" C. Gelatin is not 

 liquefied. It grows well upon agar, upon blood-serum and 

 upon Guarnieri's medium (page 75). Milk usually becomes 

 acid, and may or may not be coagulated. The colonies are seen 

 in their characteristic form upon agar, and are developed after 



* Weichselbaum in Kolle and Wassermann. Bd. III., 1903. p. 201. 



