314 BACTERIA IN CROUPOUS PNEUMONIA. 



(1889), in a case of purulent inflammation of the shoulder joint fol- 

 lowing pneumonia and pleurisy, obtained the "diplococcus pneu- 

 monise " in pure cultures. 



Morphology. Spherical or oval cocci, usually united in pairs, or 

 in chains consisting of three or four elements. Longer chains, con- 

 taining ten or more elements, are frequently formed, especially in 

 cultures upon the surface of nutrient agar, and in liquid media; it 

 may therefore be regarded as a streptococcus. As observed in the 

 blood of inoculated animals it is usually in pairs consisting of oval 

 or lance-oval elements, which are surrounded by a transparent cap- 

 sule. Owing to the elongated form of the cocci when in active 

 growth, it has been regarded by some authors as a bacillus; but in 

 cultures in liquid media, when development by binary division has 

 ceased, the cells are spherical, or nearly so, and in cultures on the 

 surface of nutrient agar the individual cells more nearly approach a 

 spherical form than in the blood of an inoculated animal. The " lan- 

 ceolate " form was first referred to by Talamon, who described it as 

 having the form of a grain of wheat, or even still more elongated 

 like a grain of barley, as seen in the fibrinous exudate of croupous 

 pneumonia. * The transparent material surrounding the cells so- 

 called capsule is best seen in stained preparations from the fibrinous 

 exudate of croupous pneumonia or from the blood of an inoculated 

 animal. It appears as an unstained marginal band surrounding the 

 elliptical cells, and varies greatly as to its extent in different prepara- 

 tions. This capsule probably consists of a 

 substance resembling mucin, and, being solu- 

 ble in water, its extent depends partly upon 

 the methods employed in preparing speci- 

 mens for microscopical examination. It is 

 occasionally seen in stained preparations from 

 the surface of cultures on blood serum ; and 

 in drop cultures examined under the micro- 



^P 6 ' b y usi "g a sma11 di^^agm it may 

 suie, attached to pus cells from be seen to surround the cocci as a scarcely 



exudate in pleura! cavity of vidihln Vialn 

 inoculated rabbit. (Salvioli.) V1S1 ^ e . nal ' 



This micrococcus stains readily with the 



aniline colors; and also by Gram's method, which constitutes an 

 important character for distinguishing it from Friedlander's ba- 

 cillus. 



Biological Characters. Grows in the presence of oxygen 

 aerobic but is also a facultative anaerobic. Like other micro- 

 cocci, it has no spontaneous movements. It grows in a variety of 

 culture media when they have a slightly alkaline reaction, but will 

 not develop in a medium which contains the slightest trace of free 



. 



