THE MENINGOCOCCUS GROUP 329 
are found in polymorphonuclear leukocytes, but never in lymphocytes 
or other body cells.^ They are intracellular but never intranuclear, 
according to Councilman, Mallory and Wright. This may be sugges- 
tive but not diagnostic. 
The organisms are non-motile and possess no flagella. No spores 
are formed and no capsules have been demonstrated. (Jaeger- 
believed that the organisms produced capsules, but his observations 
are unconfirmed.) Ordinary anilin dyes stain meningococci, but cjuite 
irregularly. Occasionally one element of a pair stains intensely 
while its fellow stains faintly or not at all. Relatively large oval or 
round forms are frequently seen in cultures and in purulent exudates 
as well, which exhibit a brightly staining point in the center of the 
organism; the remainder of the cell is scarcely colored.'' Carbol thi- 
onin is one of the best stains for the organism. The meningococcus 
is Gram-negative. Occasional organisms in subcultures upon arti- 
FiG. 44. — Meningococci in pus. X 1000. 
flcial media may decolorize with difficulty; unless extreme care is 
taken, this may lead to the conclusion that Gram-staining micrococci 
are present as contaminants. Cultures and organisms directly from 
the patient are always Gram-negative. Meningococci obtained from 
purident exudates or from cultures on artificial media cannot be 
definitely dift'erentiated from gonococci or even from Micrococcus 
catarrhalis by any known staining methods. The source of the 
material should be know^n before even a tentative morphological 
diagnosis is attempted. 
Isolation and Culture.— The meningococcus grows feebly or not at 
all upon ordinary artificial media. Growths may be obtained upon 
agar containing practically unaltered animal protein, as defibrinated 
1 Councilman, Mallory and Wright: Epidemic Cerebrospinal Meningitis. A Report 
to the Massachusetts State Board of Health, 1898, p. 75. 
2 Ztschr. f. Hyg., 1895, 19, 351. 
^ Councilman, Mallory and Wright: Loc. cit., p. 74. 
