186 SUPPURATION. 



it is an associated organism in only a very small percentage 

 of the cases of lobar pneumonia. 



Morphology and biology : The pneumobacillus is a very 

 short bacillus with rounded ends, occurring in pairs or chains. 

 The germ at times is so short as to resemble a coccus, and 

 when seen in pairs it may be mistaken for the pneumococcus. 

 In the sputum it is surrounded by a capsule. It stains with 

 all,lhe-nnilin dyes, but jiot by Gram's method. It does not 

 sporulate, is non-motile, and has no flagella. It is a faculta- 

 tive anaerobe, growing equally well at the temperature of the 

 body or the room temperature. 



On gelatin plates it forms minute porcelain-like colonies, 

 which have a very regular outline and are finely granular. 

 On agar-agar plates the colonies are much larger, moist, and 

 of a grayish color. In the gelatin stab a typical nail growth 

 is seen (Figs. 79-82). The medium is not liquefied. A thick, 

 heavy, moist growth is formed on agar slants. On potato a 

 very luxuriant yellowish growth develops which soon covers 

 the entire surface of the potato. It does not coagulate milk. 

 It causes fermentation in media containing grape-sugar or 

 milk-sugar. It produces aromatics, especially indol. Gas 

 bubbles are occasionally formed in the gelatin cultures. 



Pathogenesis : The bacillus has been found in the mouth 

 and throat of healthy individuals, in the ear, and in the 

 sputum of lobar pneumonia associated with the pneumococ- 

 cus ; also in gangrene of the lung, catarrhal pneumonia, 

 malignant endocarditis, and the conditions already mentioned. 



