210 



ACUTE PNEUMONIA. 



vigorous, ancl is more delicate in appearance. A similar 

 statement also applies to cultures in gelatine at 22 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. 

 On agar plates colonies are almost 

 invisible to the naked eye, but under 

 a low power of the microscope 

 appear to have a compact finely 

 granular centre and a pale trans- 

 parent periphery. In bouillon, growth 

 forms a slight turbidity, which settles 

 to the bottom of the vessel as 

 a slight dust -like deposit. On pota- 

 toes, as a rule, no growth appears. 

 Cultures on such media may be 

 i FlG< f 7 ^~ St i r r e maintained for one or two months, 



culture ot r raenkel s . 



pneumococcuson " hcsh sub- cultures are made every 

 blood agar. The four or five days, but they tend ul- 

 coloniesareunusually timately to die Qut They also 

 large and distinct. 



24 hours' growth at rapidly lose their virulence, so that 

 37 C. Natural size. four or five days after isolation from 

 an animal's body their pathogenic 

 action is already diminished. Eyre and Washbourne, 

 however, have succeeded in maintaining cultures in a 

 condition of constant virulence for at least three months 

 by growing the organisms on agar smeared with rabbits' 

 blood. The agar must be prepared with Witte's peptone, 

 must not be heated over 100 C., and after neutralisation 

 (rosolic acid being used as the indicator) must have . 5 . 

 per cent of normal sodium hydrate added. The tubes 

 when inoculated are to be kept at 37.5 C. and sealed to 

 prevent evaporation. In none of the ordinary artificial 

 media do pneumococci develop a capsule. They usually 

 appear as diplococci, but in preparations made from the 

 surface of agar or from bouillon, shorter or longer chains 

 may be observed (Fig. 58). After a few days' growth 



