CHAPTER XXV. 



PNEUMOBACILLUS ; FRIEDLANDER' S BACILLUS. 



DISCOVERED by Friedlander (1883), and declared by 

 him to be the cause of fibrinous pneumonia. Subse- 

 quent researches have shown that it is present in only 

 a small proportion of the cases of this disease. It is 

 found also not infrequently in the mucous membranes 

 of the mouth and air-passages of healthy individuals, 

 and in the air. 



Morphology. Short bacilli with rounded ends, often 

 resembling micrococci, especially in recent cultures; 

 commonly united in pairs or in chains of four, and, 

 under certain circumstances, surrounded by a trans- 

 parent capsule. This capsule is not seen in prepara- 

 tions made from artificial culture media, but is visible 

 in well-stained preparations from the blood of an in- 

 oculated animal. 



Friedlander' s bacillus stains readily with the aniline 

 colors, but is not stained by Gram's method. 



Biological Characters. An aerobic, non-motile, non- 

 liquefying bacillus; also facultative anaerobic; does not 

 form spores. In gelatin stick cultures it presents the 

 " nail-shaped " growth first described by Friedlander, 

 which is not, however, peculiar to this bacillus. Gas- 

 bubbles occasionally develop in gelatin, and in old 

 cultures the gelatin acquires a distinct brownish colora- 

 tion. This latter characteristic distinguishes the growth 



