CHAPTER X 
THE MENINGOCOCCUS AND PARAMENINGOCOC¬ 
CUS GROUP (MENINGOCOCCUS INTRA- 
CELLULARIS MENINGITIDIS) 
Meningitis (the inflammation of the brain coverings) 
is caused in 70 per cent by the meningococcus, in 20 per 
cent by pneumococcus, and in 10 per cent by staphylo¬ 
cocci, streptococci, Bacillus tuberculosis, Bacillus influ¬ 
enzae (grippe), etc. 
I. Historical 
Meningococcus was first observed in 1884 by Marchia- 
fava and Celli, and thoroughly studied in 1887 by Weich- 
selbaum. 
II. Morphology 
Meningococci occurs within or without the pus cells 
when isolated from the cerebrospinal fluid; they usually 
occur in pairs, like pneumococci do; they vary in size; 
they are not motile, have no flagella, no spores, no cap¬ 
sules; they stain readily with or without ordinary stains 
and are Gram-negative. 
III. Cultural Characteristics 
Meningococci do not grow well on ordinary meat ex¬ 
tract media, but grow easily on meat infusion media; 
milk is not coagulated, gelatin is not liquefied. Menin¬ 
gococcus is an aerobe, the growth not taking place below 
25° C., or above 42° C. 
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