=Gliomata= occur with almost equal frequency in cerebrum and cerebellum. They are generally primary and single, the boundaries but ill-defined, and the tumour is seldom amenable to radical surgical procedures. [Illustration: FIG. 64. AN ENDOTHELIOMA OF THE DURA MATER.] [Illustration: FIG. 65. A FIBROMA OF THE DURA MATER. Indenting the cortex and attached to the pia-arachnoid by fine filaments.] =Sarcomata= grow from the meninges, periosteum of cranial bones, and from the sheaths of nerves and vessels. They are either primary and then single, or secondary and then multiple (sarcomatosis). Sarcomata are often more or less encapsuled, tending in the first instance to exercise a compression force, and only in the later stages to invade the surrounding regions. It is during this early stage of development that the tumour is capable of removal. [Illustration: FIG. 66. AN ACOUSTIC TUMOUR. Attached loosely to the seventh and eighth nerves.] =Endotheliomata= grow from the meninges of the brain. They are hard, nodular, and, in their early stages, definitely non-infiltrating, and, when accessible, removable. =Fibromata= are especially prone to originate in the cerebello-pontine angle, usually possessing a narrow stalk representing an atrophied nerve-trunk or vascular bundle. From the frequency with which these cerebello-pontine tumours are attached to the eighth nerve they are often designated _acoustic_ tumours. They may be as small as a pea or as large as a hen’s egg. In their early stages they are probably pure fibromata, appearing as pink-red lobulated tumours. They are of slow growth, primarily compressing the brain-substance without invasion. Later on degenerative changes are prone to occur, with invasion of the cerebellar substance and extension into the internal auditory canal. Whether growing in the cerebello-pontine angle or in other parts of the skull, fibromata are often readily removed. [Illustration: FIG. 67. SYMMETRICAL TUBERCULOMATA. Situated on either side of the falx cerebri above the tentorium cerebelli.] =Tuberculomata= are most commonly situated beneath the tentorium. They are often multiple. They cannot be considered as favourable tumours from the surgical point of view, insomuch as they are frequently associated with tuberculous lesions in other parts of the body and complicated by a tuberculous infiltration of the meninges. =Syphilomata= occur with greater frequency in the cerebrum than in the cerebellum. Sometimes they are totally unaffected by anti-syphilitic remedies, and, under such conditions, appear as densely hard and definitely encapsuled tumours. These more chronic gummata are usually cortical or subcortical in position, and, when accessible, are readily removable.