CHAPTEK XXVI. 



MENINGOCOCCUS OR DIPLOCOCCUS (MICROCOCCUS) INTRACEL- 



LULARIS MENINGITIDIS, AND THE RELATION OF IT AND 



OF OTHER BACTERIA TO MENINGITIS. 



IN the description of the diplococcus of pneumonia reference was made 

 to this organism as the most frequent cause of isolated cases of meningitis, 

 especially when it complicated pneumonia. In 1887 Weichselbaum 

 discovered another micrococcus in the exudate of cerebrospinal menin- 

 gitis in six cases, two of which were not complicated by pneumonia. He 

 obtained it in pure cultures, studied its characteristics, and showed that 

 this organism was clearly distinguishable from the micrococcus lanceo- 

 latus, and especially by its usual presence in the interior of pus-cells, 

 on which account he called it diplococcus intracellularis meningitidis. 

 The frequency of the occurrence of this diplococcus in meningitis and 

 its almost complete restriction to this disease affords sufficient evidence 

 for the assumption that it was concerned in its production. In 1895 

 Jaeger and Scheurer believed they found it in the nasal secretions of 

 eighteen living persons suffering from this disease during an epidemic. 



It seems very probable that in most cases of primary meningitis it 

 is from the mucous membrane of the nasal cavities and the sinuses 

 opening out from them that both the diplococcus of pneumonia and 

 the micrococcus intracellularis find their way through the lymph chan- 

 nels to the meninges. The former we know to be almost constantly 

 present in the nasal cavities, and the latter we have reason to believe 

 is not infrequently there. The prevalence of epidemics in winter and 

 spring, a time favorable to influenza and pneumonia, also suggests the 

 respiratory tract as the source of the infection and the place where an 

 increase in virulence takes place. We do not as yet know why menin- 

 gitis follows in some persons and not in others after infection of the 

 mucous membranes. 



The meningococcus dies readily when dried, so that we seldom inhale 

 it except in rooms occupied by those infected. Such persons and 

 things recently soiled by their nasal secretion are especially dangerous. 



Morphology. This organism occurs as biscuit-shaped micrococci, 

 usually united in pairs, but also in groups of four and in small masses; 

 sometimes solitary and small degenerated forms are found. Cul- 

 tures resemble strongly those of gonococci (see Fig 1 . 111). In cultures 

 more than twenty-four hours old larger and smaller forms occur and 

 some which stain poorly. These are involution forms. In the exu- 

 dation, like the gonococcus, to which it bears a close resemblance in 

 form and arrangement, it is distinguished by its presence, as a rule, 



