CHAPTER XIV. 
THE MENINGOCOCCUS-GONOCOCCUS-CATARRHALIS 
GROUP. 
The Meningococcus Group. I The Gonococcus Group. 
Micrococcus Meningitidis. Micrococcus Gonorrhese. 
Parameningococci. I Micrococcus Catarrhalis. 
THE MENINGOCOCCUS GROUP. 
Micrococcus Meningitidis. —Synonyms.— Diplococcus intracellularis 
meningitidis; Diplococcus weichselbaumii, Meningococcus. 
Historical.— Micrococcus meningitidis was isolated in pure culture 
by Weichselbaum^ from purulent cerebrospinal fluids of several typi- 
cal cases of cerebrospinal meningitis. The injection of pure cultures 
of the organisms directly into the meninges of dogs resulted in well- 
marked meningeal inflammation and encephalitis, von Lingelsheim 
and Leuchs- and Flexner'' have reproduced typical meningeal inflam- 
mation by the direct injection of the virus into the cerebrospinal 
axis of monkeys. Other organisms, as pneumococci, streptococci, or 
Bacillus influenzae, for example, may incite inflammations of the 
cerebrospinal membranes, but these bacteria do not ordinarily cause 
epidemics of the disease. The meningococcus frequently causes 
widespread epidemics, and, unlike the organisms just mentioned, 
(except the pneumococcus occasionally) the typical lesions are primarily 
of the cerebrospinal axis. The fact must not be overlooked, however, 
that the organisms occur in the blood stream in fully one-half of all 
cases."* The idea is gaining ground that cerebrospinal fever is pri- 
marily a blood infection. 
Morphology.— Meningococci obtained directly from the cerebro- 
spinal fluid or from meningeal exudates occur characteristically in 
pairs with their apposed sides flattened and somewhat elongated. 
They measure about 1 micron in diameter, although the size varies 
even in the same culture. The individuals are fairly uniform in size 
and shape in very young, fresh cultures, but in older cultures con- 
siderable variations in size are met with. Examined directly in 
inflammatory exudates from the spinal fluid or meninges during the 
acute stages of the disease, the organisms occur typically and char- 
acteristically as intra- and extracellular diplococci and tetrads. They 
1 Fortschr. d. Med., 1887, 5, 125, 620. 
2 Klin. Jahrb., 1906, 15, 489. 
3 Jour. Exp. Med., 1907, 9, 142. 
* Herrick: Arch. Int. Med., 1918, 21, 541. 
