THE PNEUMOCOCCUS AND PNEUMONIA 443 



Aerobic and anaerobic conditions both permit the growth of 

 pneumococcus, there being very little difference in speed or extent 

 of growth along the course of deep stab cultures in favorable media. 

 The most favorable reaction of media for the cultivation of this 

 microorganism is a P H of 7.6 to 7.8. Slight acidity, however, if not 

 exceeding eight-tenths per cent, does not materially hamper develop- 

 ment. 



The broth or agar basis for pneumococcus media must be care- 

 fully made, both in regard to nutrient contents and reaction. Ordi- 

 nary meat extract media are not usually rich enough, and even 

 carelessly made meat infusion broth may fail to grow pneumococci. 

 In our laboratory we have come to use the "hormone" broth and 

 agar media almost entirely for pneumococcus and streptococcus 

 work. 



The growth of pneumococci on all media may be considerably 

 enhanced by the addition to these media of animal or human serum 

 or whole blood. Additional substances which, among others, 

 unquestionably have a favorable influence upon pneumococcus 

 growth, are glucose, nutrose, and glycerin. The addition of the 

 latter substances to the media, however, probably because of acid 

 formation, hastens the death of pneumococcus cultures. An increase 

 of the amount of pepton used for the preparation of media is desir- 

 able for the cultivation of this microorganism; two to four per cent 

 of pepton may be found advantageous. 



Transfer of recently isolated penumococcus from broth culture 

 to broth culture necessitates rather heavy inoculation, since frequent 

 failure is experienced when only a loopful or so is transferred. Cole 

 mentions that about 0.1 c.c. should be transferred for every 5 c.c. of 

 broth. 



In suitable nutrient broth, growth is rapid, and within twenty- 

 four hours leads to slight clouding of the fluid. This clouding, as a 

 rule, eventually disappears as the microorganisms, sinking to the 

 bottom of the tube or disintegrating, leave the fluid more or less clear. 

 In broth, pneumococci have a tendency to form short chains. When 

 glucose has been added to the broth, growth is more rapid and profuse, 

 but considerable acid formation causes the cultures to die out rapidly. 

 It is possible, however, to employ glucose as a growth-enhancing ele- 

 ment in broth cultures without interfering with the viability of the 

 cultures by adding small quantities (one per cent) of sterile, powdered 

 calcium carbonate. This method of cultivation in broth is especially 



