CHARACTERS OF THE PNEUMOCOCCUS 227 





A? 



/ V * 



The general result of all observations on pneumonia has been 

 to establish that the organism described by Fraenkel and now 

 known as the pneumococcus, is that of most frequent occurrence ; 

 it is the sole organism present in about 95 per cent, of cases of 

 lobar pneumonia. 



Microscopic Characters of the Pneumococcus. — Met/tods. — 

 The organisms present in acute pneumonia can best be examined 

 in film preparations made from pneumonic lung (preferably 

 from a part in a stage of acute congestion or early hepatisation), 

 or from the gelatinous parts of pneumonic sputum (here again 

 preferably when such sputum is either rusty or occurs early in the 

 disease), or in sections of 

 pneumonic lung. Such 

 preparations are best 

 stained by Gram's method, 

 with Bismarck-brown or 

 Ziehl - Neelsen carbol- 

 fuchsin (one part to thirty 

 of water) as a contrast 

 stain ; with the latter it 

 is best either to stain for 

 only a few seconds, or to 

 overstain and then de- 

 colorise with alcohol till 

 the ground of the pre- 

 paration is just tinted ; in 

 this way the capsules can 

 often be demonstrated. 

 The capsules can also be 

 stained by the methods 

 already described (p. 107). 

 In such preparations as 

 the above, and even in specimens taken from the lungs immedi- 

 ately after death (as may be quite well done by means of a 

 hypodermic syringe), putrefactive and other bacteria may be 

 present. Similar methods are applicable to the numerous other 

 lesions besides pneumonia in which the pneumococcus occurs. 



The pneumococcus occurs in the form of a small oval coccus, 

 about 1 ft, in longest diameter, arranged generally in pairs 

 (diplococci), but also in chains of four to ten (Fig. 57). The 

 free ends are often pointed like a lancet, hence the term 

 diplococcus lanceolatus has also been applied to it. These cocci, 

 in their typical form, have round them a capsule, which, in 

 films stained by ordinary methods, usually appears as an 



I 

 I 



Fig. 57. — Film preparations of pneumonic 

 sputum, showing numerous pneumocooci 

 (Fraenkel's) with unstained capsules ; some 

 are arranged in short chains. See also 

 Plate I., Fig. 2. 

 Stained with carbol-fuchsin. x 1000: 



