CHAPTER XXV. 
PNEUMOBACILLUS ; FRIEDLANDER’S BACILLUS. 
DiscovereED 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. 
Friedlinder’s bacillus stains readily with the aniline 
colors, but is not stained by Gram’s method. 
Biological Characters. An aérobic, non-motile, non- 
liquefying bacillus; also facultative anaérobic; 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 
