302 



BACTERIA IN CROUPOUS PNEUMONIA. 



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

 ing pneumonia and pleurisy, obtained the " diplococcus pneumonise " 

 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 sometimes formed, especially in 

 cultures upon the surface of nutrient agar, and 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 capsule. Owing to the elon- 

 gated 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 indivi- 

 dual cells more nearly approach a spherical form than in the blood 

 of an inoculated animal. The " lanceolate " 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 pre- 

 parations from the fibrinous exudate of croupous pneumonia or from 

 the blood of an inoculated animal. It appears as an unstained mar- 

 ginal band surrounding the elliptical cells, and varies greatly as to 

 its extent in different preparations. This capsule probably consists 

 of a substance resembling mucin, and, being soluble in water, its ex- 

 tent depends partly upon the methods employed in preparing speci- 

 mens for microscopical examination. It is occasionally seen in 



stained preparations from the surface of cul- 

 tures on blood serum ; and in drop cultures 

 examined under the microscope, by using a 

 small diaphragm, it may be seen to surround 

 the cocci as a scarcely visible halo. 



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 bacillus, 

 with which it has often been confounded on 

 account of the morphological resemblance of 

 the two microorganisms. 

 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 



FIG. 93. Micrococcus pneu- 

 monise crouposae, showing cap- 

 sule, attached to pus cells from 

 exudate in pleural cavity of 

 inoculated rabbit. (Salvioli.) 



