PNEUMONIA. Ill 



but recognized afterward as a bacillus. It is found : a. in a 

 number of cases of pneumonia in the fibrinous exudate, 6. in 

 the blood, and c. in the sputum. 



Morphology. Short rods, with rounded ends, united in 

 pairs, sometimes in fours, having a decided capsule when 

 taken directly from the blood of the animal. When grown 

 on artificial media the capsule disappears. Occasionally the 

 capsule surrounds each individual cell, at other times it is 

 around the cells, united in pairs or fours. This capsule may 

 be distinctly brought out by the special method of staining 

 capsules mentioned in the chapter on staining. 



The Bacillus pneumonias stains well with all anilin dyes, 

 but does not stain well by Gram's method a diagnostic 

 point differentiating it from the Micrococcus pneumonice. 



Biologic Characters. It is aerobic and facultative anaerobic, 

 non-motile, and has no flagella. It grows in all the media at a 

 temperature of between 16 and 20 C., but grows best at 

 the temperature of the blood, 37 C. Growth ceases at a 

 temperature exceeding 46 C. Its growth in cultures is 

 exceedingly long lived, so that after a year or longer it has 

 grown upon transplantation into a suitable culture. 



Its growth in bouillon is cloudy. It does not liquefy gela- 

 tin. Stab-cultures in gelatin have quite a characteristic 

 appearance, growing in the form of a nail. The head of the 

 nail is at the point where the inoculating needle enters the 

 gelatin, the path of the needle through the gelatin marking 

 the body of the nail. The head of the nail is a white mass 

 of shiny appearance ; the body is opaque and made up of 

 white spherical colonies. It produces bubbles of gas in gela- 

 tin. On gelatin plates colonies appear in twenty-four hours 

 as small white spheres which increase rapidly in size, and in 

 a short time on the surface of the plate large masses are 

 formed. 



Its growth on agar is much like that on gelatin. On 

 blood-serum the growth is abundant, viscid, and grayish white 

 in color. On potato it grows rapidly and abundantly, and is 

 yellowish white in appearance. 



Pathogenesis. The Bacillus pneumonias is fatal to mice and 



