190 ACUTE PNEUMONIA. 



recommended. A valuable means is thus afforded of 

 distinguishing it from Fraenkel's pneumococcus in micro- 

 scopic preparations. 



Friedlander's organism is much less frequently present 

 in pneumonia than Fraenkel's ; sometimes it is associated 

 with the latter, rarely it occurs alone. 



In sputum preparations the capsule of both pneumococci 

 may not be recognisable, and the same is sometimes true 

 of lung preparations. This is probably due to changes 

 which occur in the capsule as the result of changes in the 

 vitality of the organisms. Sometimes the difficulty of 

 recognising the capsule when it is present, is due to the 

 refractive index of the fluid in which the specimen is 

 mounted being almost identical with that of the capsule. 

 This difficulty can always be overcome by having the 

 ground-work of the preparation tinted. 



The Cultivation of Fraenkel's Pneumococcus. It is 

 usually difficult, and sometimes impossible, to isolate this 

 coccus directly from pneumonic sputum. On culture media 

 it has not a vigorous growth, and when mixed with other 

 bacteria it is apt to be overgrown by the latter. To get a 

 pure culture it is best to insert a small piece of the sputum 

 beneath the skin of a rabbit or a mouse. In about forty- 

 eight hours the animal will die, with its blood containing 

 capsulated pneumococci. From the heart-blood, cultures of 

 these can be easily obtained. Cultures can also be got 

 post mortem from the lungs of pneumonic patients. Here 

 it is best to streak a number of agar or blood-agar tubes 

 with a scraping taken from the area of acute congestion or 

 commencing red hepatization, and incubate them at 37 C. 

 The colonies of the pneumococcus appear as almost trans- 

 parent small discs which have been compared to drops of 

 dew. This method is also sometimes successful in the 

 case of sputum. 



The pneumococcus grows best on blood serum or on 

 Pfeiifer's blood-agar. It also grows well on ordinary agar 

 or in bouillon or on gelatine (incubated at 22 C.), but not 

 so well on glycerine agar. In a stroke culture on blood 



