284 STREPTOCOCCUS-PNEUMOCOCCUS GROUP 



blood into 100 to 150 c.c. of 0.1 per cent, dextrose broth, and incubating 

 for twenty-four hours at 37 C. Isolation of pneumococci from sputum 

 by cultural methods is practically hopeless; but pure cultures may 

 be obtained from the heart blood of white mice inoculated subcutan- 

 eously with sputum. 



The organisms may be obtained from inflammatory exudates and 

 pus either by inoculation of the material into white mice or infecting 

 the surface of blood agar, serum, ascitic or hydrocele agar plates. 

 Colonies on blood agar plates are minute, gray, and surrounded by a 

 greenish halo which Butterfield and Peabody 1 and Cole 2 have shown 

 to be methemoglobin. Colonies on ascitic agar are small, transparent 

 and colorless. The growth upon plain nutrient agar or gelatin is very 

 scanty. Gelatin is not liquefied. The addition of dextrose to agar 

 increases the nutritive value of the medium, but the acid formed by 

 the fermentation of the dextrose soon kills the bacteria unless calcium 

 carbonate is added to neutralize the acid. Many strains of pneumo- 

 cocci grow in milk, producing as a rule sufficient acid to cause coagula- 

 tion. The coagulum is never liquefied. Growth upon Loffler's blood 

 serum is moderately luxuriant, particularly for subcultures; initial 

 development of the organisms directly from human or animal sources 

 is not extensive upon this medium. The colonies are small, clear and 

 colorless, and not distinctive. Growth is more rapid in fluid than 

 in solid media. Secondary inoculations into plain broth or broth 

 containing utilizable carbohydrates result in a clouding of the medium 

 and extensive development, more luxuriant in the latter than the 

 former. The addition of blood, blood serum or ascitic fluid to media 

 increases the nutritive value greatly. The organisms die within a 

 few days, and even after twenty-four hours' incubation degenerative 

 forms appear, and they become Gram-negative. Transfer at frequent 

 intervals to fresh media is essential to maintain viable cultures of the 

 pneumococcus. 



The pneumococcus is an aerobic, facultatively anaerobic organism 

 whose limits of growth lie between 25 C., below which development 

 ceases, and about 42 to 43 C.; the optimum temperature of growth 

 is 37 C. The organisms are not resistant to heat, being killed by an 

 exposure of ten to fifteen minutes to 55 C. 3 Chemical disinfectants, 

 as 5 per cent, carbolic acid or 1 to 1000 bichloride of mercury, destroy 

 pneumococci readily. Dried rapidly in sputum, they retain their 



1 Jour. Exp. Med., 1913, xvii, 587. 



2 Ibid., 1914, xx, 363. 



3 See Wood, Jour. Exp. Mod., 1905, vii, 592, for literature. 



