Disputatio de phrenitide

Pliny, book 7, chapters 50 and 51.

an apostema an abscess or gathering of pus in the brain or its coverings. Pliny, in book 7, chapters 50 and 51, called it a sickness of wisdom. Celsus calls it mania with fever. Other Latins use the Greek name, phrenitis.

V.
Sometimes this name is placed (as Avicenna wishes, Fen 3, tract 3, chapter 1) for the symptom, namely for the injured action itself. In this signification, the author of the book De fin.? received it when he says it is a continuous delirium with continuous fever; and Avicenna in the aforementioned place when he says it is an alienation and permission of the intellect with scorching heat. Sometimes, however, it is taken for the preternatural disposition of the brain, which exists as the cause of this symptom.

VI.
This preternatural disposition, both Greeks and Arabs unanimously establish as an inflammation of the brain. But since the whole brain consists of two parts, namely the membranes and the substance of the brain, it is doubtful whether the membranes or the substance of the brain are inflamed.

VII.
For there are those (as Paulus and certain other most famous recent physicians) who try to prove that an inflammation cannot exercise itself upon a body that is neither soft, like the brain, nor hard, like the teeth. For it is necessary (they say) that bodies which are to be inflamed must be extensible, so that they can receive and retain the matter flowing toward them. The substance of the brain, however, since it is full of small holes, cannot retain bilious humors, which are very thin. Therefore, it cannot arise in the brain itself, but in the membranes, which, because they are solid and extensible bodies, are most apt for inflammation.

VIII.
Rases, Serapio, and Auenzoar agree with this opinion, except for the fact that Rases, in the first book of the Continens a medical encyclopedia, asserts that the pia mater, since its substance is soft and filled with veins and arteries, and because of this is hotter, is more prone to inflammation.

Auenzoar