THE PNEUMOCOCCUS 319 
by the fermentation of the glucose soon kills the bacteria unless 
calcium carbonate is added to neutralize the acid. Many strains of 
pneumococci grow in milk, producing as a rule, sufficient acid to 
cause coagulation. The coagulum is never liquefiefl. Growth upon 
Loffler's blood serum is moderately luxuriant, particularly for sub- 
cultures; 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 
rai)id 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 bloofl, 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 tend to become 
Gram-negative. Transfer at frequent intervals to fresh media is 
essential to maintain viable cultures of the pneumococcus. Avery, 
however, has kept pneumococci alive for many weeks dried in the spleen 
of mice which have died of infection induced by inoculation with pure 
cultures. 
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.^ 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 
viability for nearly two weeks, but sunlight is rapidly fatal. The 
virulence is rapidly lost during cultivation in artificial media, but it 
may be retained practically unimpaired for weeks if the organisms 
suspended in blood are sealed in glass tubes and maintained in the 
dark at ice-box temperature. Pneumococci obtained from sputum, 
either of healthy individuals or from the "rusty sputum" character- 
istic of the earlier stages of lobar pneumonia, possess sufficient viru- 
lence to kill white mice. The original virulence frequently may be 
restored to cultures on artificial media by passage through white 
mice, provided large doses are administered at the start. Repeated, 
rapid inoculations of virulent pneumococci frequently lead to a decided 
increase of virulence above that originally exhibited by the organisms. 
Products of Growth. — r/;e/?am/.— The pneumococcus produces acids, 
chiefly lactic, but smaller amounts of acetic and formic acid in hexoses, 
bioses and many starches. Hiss, Borden and Knapp^ have shown that 
the fermentation of inulin by the pneumococcus is a fairly constant 
cultural dift'crentiation of the organism from the streptococcus, which 
is apparently ordinarily unable to ferment this starch. This test 
1 See Wood: Jour. Exp. Med., 1905, 7, 592, for literature. 
2 Jour. Exp. Med., 1905, 7, 547. 
