230 THE ACUTE PNEUMONIAS 



involution forms appear, usually in the form of pointed rods due 

 to elongation of a coccus -without division. Usually the pneu- 

 mococcus does not grew below 22° C, but forms in which the 

 virulence has disappeared often grow well at 20° C. Its 

 optimum temperature is 37° C, its maximum 42° C. It is 

 preferably an aerobe, but can exist without oxygen. It prefers 

 a slightly alkaline medium to a neutral, and does not grow 

 on an acid medium. In ordinary media, as just stated, 

 the pneumococcus does not usually appear to develop a capsule, 

 but, according to Hiss, the absence of a capsule is often only 



apparent, and if in mak- 



\ ing cover-glass prepara- 



*• i * 1 " „ tions off such media some 



/ /» f"** ^ *\ serum be used as the 



* % **> diluent, and the films 



^ ' _» t ^ stained be by his copper- 



/. • v ., ^ ^ i sulphate method (p. 



l' t \ . j I ^ 107), a capsule can be 



*" 1 demonstrated. Capsula- 



v " ** \ .' tion frequently appears 



s *-* s in fluid serum media, 



' s « \ e.g., if the organism be 



grown in rabbit or human 

 serum which has been 

 obtained under aseptic 

 precautions and heated 



i_ x /' serum which has been 



■■^ obtained under aseptic 



Fig. 60. — Fraenkel's pneumococcus from a pure for half an hour at 55° C. 



culture on blood agar of twenty-four hours' <slnnp=i over 



growth, some in pairs, some in short chains. 0r , . 0n a S ar S10 P? S 0Ver 



Stained with weak carbol-fuchsin. xlOOO. which a drop of serum 



has been run. 

 The pneumococcus is non-hasmolytic on blood-agar plates 

 (p. 45), and it ferments saccharose, raffinose, and lactose; 

 a similar fermentative action on inulin is important, as 

 ordinary streptococci do not ferment this sugar. Apparently 

 some samples of inulin are more readily acted on than others. 

 Usually the test is carried out with Hiss's inulin serum water 

 medium, in which coagulation of the serum results (p. 46), but 

 some investigators have had more success with inulin bouillon, 

 acid production being estimated , by titration against soda with 

 a phenolphthalein indicator. 



The pneumococcus is soluble in bile. To demonstrate this, 

 fresh ox bile autoclaved for twenty minutes at 120° C. and filtered 

 is added to a fully developed fluid culture (which must be one in 

 simple bouillon) in the proportion of about a fifth of the 



