CHARACTERS OF BACTERIA OF PNEUMONIA. 207 



Weichselbaum's diplococcus pneumoniae, and probably also 

 with his streptococcus pneumoniae. 



2. Friedlander 's pneumococcus (now known as Fried- 

 lander's pneumobacillus), which is almost certainly the 

 same as the bacillus pneumoniae of Weichselbaum. 



We shall use the terms " Fraenkel's pneumococcus " and 

 " Friedlander's pneumobacillus," as these are now usually 

 applied to the two organisms. 



Microscopic Characters of the Bacteria of Pneumonia. 

 Methods. The organisms present in acute pneumonia can 

 best be examined in film preparations made from pneu- 

 monic lung (preferably from a part in a stage of acute con- 

 gestion or early hepatization) 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 may be stained by 

 any of the ordinary weak stains, such as a watery solution 

 of methylene-blue, but Gram's method is to be preferred, 

 with safranin or Bismarck-brown as a contrast stain. Ziehl- 

 Neelsen carbol-fuchsin is also very suitable ; it is best either 

 to stain with it for only a few seconds, or to overstain and 

 then decolorise with alcohol till the ground of the prepara- 

 tion is just tinted. In such preparations as the above, and 

 even in specimens taken from the lungs immediately after 

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

 syringe), putrefactive and other bacteria may be present, 

 but those to be looked for are capsulated organisms which 

 may be of either or both of the varieties mentioned. 



(i) FraenkeFs Pneumococcus. This organism occurs in 

 the form of small oval cocci, about i /A in longest diameter, 

 arranged generally in pairs (diplococci), but also in chains 

 of four to ten (Fig. 56). The free ends are often pointed 

 like a lancet, hence the term diplococcus lanceolatus has also 

 been applied to it. These cocci have round them a capsule, 

 which usually appears as an unstained halo, but is some- 

 times stained more deeply than the ground of the prepara- 

 tion. This difference in staining depends, in part at 

 least, on the amount of decolorisation to which the pre- 



