THE MENINGOCOCCUS GROUP 333 
the disease; middle-ear involvement is comparatively frequent. The 
nasopharynx appears to be the normal habitat of the meningococcus; 
the organism is almost invariably found at this point in the earlier 
stages of the disease. Organisms from the nasopharynx and from the 
spinal fluid are practically always of the same type or group. It is 
probable that the organism passes from the nose and nasopharynx 
directly into the blood stream, and later through the lymphatics to the 
base of the brain. The accessory sinuses of the nasal cavity appear 
to be inflamed in a majority of cases, particularly during the initial 
clinical period of the disease. There is a thickening of the meninges 
in those cases which run a more chronic course, frequently with con- 
siderable distention of the ventricles. Intracranial pressure is usually 
a prominent symptom. The organism has been isolated from the blood 
by Jacobitz,! Dieudonne,^ Elser,'' and Elser and Huntoon,* the latter 
in 25 per cent of their large series of cases and Herrick {he. cit.) in about 
50 per cent of his cases. 
Holm and Da\'ison^ found, also, that meningococci were important 
incitants of postinfluenzal pneumonia, the types being the same as 
those found in the spinal fluids in cases of epidemic cerebrospinal 
meningitis. 
, Immunity and Immunization.— There is very little definite informa- 
tion concerning the resistance of man to infection with the meningo- 
coccus. The disproportionately large ratio of carriers to cases observed 
in nearly every epidemic of the disease which has been carefully 
studied, suggests that the organism possesses feeble invasive power 
for the normal individual. The nasopharyngeal secretion and the 
saliva appear to be rather poor culture media for its growth under 
normal conditions and it is not improbable that intracurrent inflam- 
mation of the nasopharyngeal membrane may be a factor in deter- 
mining infection. Common colds, adenoids and similar abnormalities, 
and even catarrhal inflammation of the nasopharyngeal mucosa,*^ may 
be of some ancillary importance in establishing conrlitions favorable 
to invasion of the meninges. The cerebrospinal fluid and normal 
blood serum are distinctly bactericidal to meningococci.^ 
The blood serum of normal, uninfected individuals and e^'en of 
meningococcus carriers is almost always devoid of agglutinins, lysins, 
or opsonins which will react in significant dilution with the homol- 
ogous type of organism. There is some evidence that the serum of 
chronic carriers will exhibit specific complement-fixation with the 
homologous type of organism. 
Attempts to increase resistance to infection in experimental animals 
1 Miinchen. med. Wchnschr., 1905, 52, 2020, 2178. 
2 Centralbl. f. Bakteriol., orig., 1906, 41, 418. 
3 Jour. Med. Res., 1906. 14, 89. < Ibid., 1909, 20, 371. 
6 Johns Hopkins Hosp. Bull., 1919, 30, 324, 329. 
8 There is some evidence that the meningococcus itself may produce a catarrhal 
inflammation of the nasopharynx. 
' Davis: .Jour. Infec. Dis., 1905, 2, 602. 
