CULTIVATION OF PNEUMOCOCCTJS 229 



that of the capsule. This difficulty can always be overcome by 

 having the groundwork 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 mm isc. In about twenty-four to forty -eight hours the 

 animal will die, with numerous capsul- 

 ated pneomooocci throughout its blood. 

 K PI 111 the heart-blood cultures can be 

 easily obtained. Cultures can also be 

 got post mortem from the lungs of 

 pneumonic patients by streaking a 

 number of agar or blood-agar tubes with 

 a scraping taken from the area of acute 

 congestion or commencing red hepatisa 

 tion, and incubating them at 37 ('. 

 The colonies of the pneumococcus appear 

 as almost transparent small discs which 

 have been compared to drops of dew 

 (Fig. 65). This method is also some- 

 times successful in the case of sputum. 



The appearances presented in cultures Fro . K ._ St roke culture of 

 by different varieties nt the pneuino- Fraenkel's pneumococcus 

 coccus vary somewhat. It always grows n Mow I agar. The 

 best l,l,,o,l son,,,, ,, l>,ViHer' S !*&?** 

 blood agar. It usually grows well on four hours' growth at 

 ordinary agar or in bouillon, but not :;7 r - Natural size. 

 BO well on glycerin agar. In a stroke 



culture on hlood serum, growth appears as an almost trans- 

 parent pellicle along the track, with isolated colonies at the 

 margin. On agar media it is more manifest, but otherwise 

 has similar characters. On agar plates colonies are very 

 transparent, but under a low power of the microscojK3 appear 

 to have a compact finely granular centre and a pale trans- 

 parent periphery. The appearances arc similar to those of 

 a culture of streptococcus pyogenes, but the growth is less 

 vigorous, and is more delicate in appearance. A similar 

 statement also applies to cultures in f/elatin at 2'2 C., growth 

 in a stab culture appearing as a row of minute points which 

 remain of small size; there is, of course, no. liquefaction of the 

 medium. In bouillon, growth forms a slight turbidity, \\hich 



