BIOLOGY OF PNEUMOCOCCUS 37 



tissue, protein of comparatively small molecular size in the form of 

 peptone, a small amount of sugar, mineral salts, and a suitable 

 concentration of hydrogen ions. All media should be subjected to 

 the least degree of heat necessary to effect extraction of the meat, 

 to render the ingredients soluble, and to ensure final sterility. 



The earlier bacteriologists employed the only media known in 

 their time, such as egg albumen (Klebs 718 ), veal or beef broth 

 (Pasteur), then broth with the addition of gelatin or agar (Fried- 

 lander 487 ) and later of blood (Nissen, 1013 and Gilbert and Four- 

 nier, 513 among others), serum, or other body fluids. Fraenkel 469 

 employed milk, but finding the cocci lost virulence on this medium, 

 turned to coagulated blood serum and then to meat-infusion agar. 

 Eggs, both in the shell (Bunzl-Federn 186 ), inspissated, and as a 

 base with broth (Gaskell 499 ) have been employed for the mainte- 

 nance of virulence, while Grawitz and Steffen 547 preferred co- 

 agulated sputum as a favorable medium for capsule formation. 

 Schmidt 1236 also recommended sputum as a medium on which 

 Pneumococcus developed clear, well-formed capsules, and which 

 also would restore capsules to cocci that had lost them after culti- 

 vation on agar. Gilbert and Fournier 513 found defibrinated blood of 

 man and other animals to be suitable for the propagation of pneu- 

 mococci. Carnot and Fournier 200 noted constancy of virulence and 

 capsule formation of strains grown in broth and on agar contain- 

 ing brain tissue, but the fluid medium could be employed only for 

 the carrying on of pure cultures. 



Among the great variety of nutrient materials recommended, 

 time and experience have shown the essential ones, and these are 

 now incorporated into a few formulas which meet all the needs of 

 the student of Pneumococcus.* While Pneumococcus can be grown 

 within a fairly wide range of cultural conditions, the most vigor- 

 ous and viable individuals are obtained when careful attention is 

 given to the needs peculiar to this organism. Fresh beef, veal, or 



* See Appendix. 



