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.
Fig. 64. An Endothelioma of the Dura Mater.
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.
Fig. 66. An Acoustic Tumour. Attached loosely to the seventh and eighth nerves.