Attempts have been made to classify the various forms of meningitis on a bacterial basis. When, however, it is realized that almost any known form of organism may be present in the exudate, and that the symptoms dependent on these various infections closely resemble one another, merely differing in their acuteness and intensity, it would appear that some other form of classification is preferable.
The following method of classification will suffice:—
1. Meningitis of traumatic origin.
The organisms either obtain direct entrance to the meningeal space by means of a compound fracture of the vault or base of the skull, or reach their destination along the course of the numerous emissary and diploic veins that bring the extra- and intra-cranial channels into communication.
2. Meningitis secondary to disease of neighbouring regions.
(1) The accessory sinuses of the nose and ear.
(2) The bones of the skull.
(3) The soft parts—scalp, orbit, nose, and face.
3. Meningitis secondary to disease of more distant regions.
Through the medium of the blood-stream bacteria may be carried to the meningeal region in many acute infections—more especially in diseases of the lung.