CHAPTER XXIV 



MICROCOCCUS INTRACELLULARIS MENINGITIDIS 

 (MENINGOCOCCUS) 



Infectious processes in the meninges may be caused by many dif- 

 ferent microorganisms. 



Meningitis may be primary or secondary. Secondary meningitis 

 may often occur during the course of pneumonia, when pneumococci, 

 carried to the meninges by the blood stream, give rise to a usually fatal 

 form of the disease. More rarely a similar process may occur as a 

 secondary manifestation of typhoid fever or influenza. Meningitis may 

 also result secondarily by direct extension from suppurative lesions about 

 the skull, such as those occurring in diseases of the middle ear or frontal 

 sinuses or after compound fractures. In such cases the invading or- 

 ganisms are usually staphylococci, streptococci, or pneumococci. 



Isolated cases of meningeal infection with B. coli, B. paratyphosus. 

 Bacillus pestis, and Bacillus mallei have been reported. A frequent, 

 more chronic form of the disease is caused by Bacillus tuberculosis. 



Primary acute meningeal infection, however, is due chiefly to two 

 microorganisms, Micrococcus intracellularis meningitidis, and the pneu- 

 mococcus. 



A tabulation of the comparative frequency with which the various 

 microorganisms are found in the meninges has been attempted by 

 M^rschal.' This author estimates that about 69.2 per cent of all 

 acute cases are due to the meningococcus, 20.8 per cent to Diplococcus 

 pneumonige, and the remaining 10 per cent to the other bacteria 

 mentioned. 



The cases caused by the pneumococcus and the other less frequent 

 incitants usually occur sporadically. When the disease occurs in epi- 

 demic form, it is almost always due to the meningococcus. 



Diplococcus intracellularis meningitidis was first seen in menin- 

 geal exudates by Marchiafava and Celli ^ in 1884. These authors not 

 only described accurately the morphological characteristics now recog- 



' Marschal, Diss. Strassburg, 1901, Quoted from Weichselbaum, in KoUe und 

 Wassermarm, " Handbuch." 



2 Marchiafava and Cetti, Gaz. degli ospedali, 8, 1884. 



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