CHAPTER XXIX. 
DIPLOCOCCUS INTRACELLULARIS MENINGITIDIS. 
In the description of the micrococcus lanceolatus 
reference was made to this organism as the most fre- 
quent cause of meningitis, especially when it compli- 
cated pneumonia. In 1887, Weichselbaum discovered 
another micrococcus in the exudate of cerebro-spinal 
meningitis in six cases, two of which were not com- 
plicated 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 occur- 
rence of this diplococcus in meningitis and its restric- 
tion to this disease affords sufficient evidence for the 
assumption that it was concerned in its production. 
In 1895, Jaeger and Scheurer found it in the nasal 
secretions of eighteen living persons suffering from this 
disease during an epidemic. 
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 
smaller degenerated forms are found. In the exuda- 
tion, like the gonococcus, to which it bears a close re- 
semblance in form and arrangement, it is distinguished 
by its presence within the polynuclear leucocytes. It 
