Excerpted from De proprietatibus rerum 5.3

The brain, as Constantinus [Africanus] says in the Pantegni book 2, chapter 11, is a white body, also without blood, which has much of the soul and also of marrow. It is divided into three parts. It is the beginning of all of the strength of the body. It is secured below two protective layers, one like a tender and the other a hardy mother. It is placed in the top of the head, as this is the best part of the body. Moreover, the brain is naturally white so that it is a ready place for receiving the likeness of any body. It has much of the soul, with the result that there is much motion in it. And it also has much of the marrow, so that the high heat generated from its motion may be tempered. But it has only a little of the blood, so that it is not stained by its color, for this would make all apprehensions seem red. Therefore it is also moist without blood, so that it can swiftly be altered in its nature for the purpose of perception. So says Constantinus.  There is however a distinction between the three chambers of the brain, because the brain has three cavities, which are called ventricles by scientists. In the back chamber or ventricle the imagination is shaped, in the middle region reason, and in the next memory and recollection.

Original Latin

Ad defensionem autem cerebri fuerunt necessari duo panni, qui vocantur matres cerebri. Unus est grossus, scilicet dura mater. Hic cranio supponitur, sed in medio cerebro ingrossatur, et ad maiorem fortitudinem solidatur, non tamen immediate cum craneo coniungitur, immo potius suspenditur, et huc atque illuc circa cerebri substantiam dilatatur. Secundus panniculus dicitur pia mater, quae durae matri supponitur, quae mollior est dura matre. Unde substantiam cerebri circumvolvit et per dictas cellulas ab invicem separat et discernit.

Homo inter omnia animalia suae quantitatis maximum habet cerebrum, quia cor maximi est caloris. Unde propter caloris dominium et bonitatem complexionis est homo boni intellectus, et intelligentior cunctis animalibus, et non possunt infantes longo tempore portare caput rectum propter magnitudinem et ponderositatem, donec a calore cordis mediantibus arteriis a suo pondere allevietur.

Bona vero dispositio cerebri, sicut et mala, per suas cognoscitur actiones. Nam si fuerit substantia cerebri mollis, clara ac pervia, de facili recipit formarum impressiones et sigillationes. Unde propter velocitatem sigillationis, formarum, rerum, est habens causam bonae et velocis disciplinae. Quando vero e converso est non mollis vel turbida, habens causam durius et tardius recepit impressionem vel impressiones.

Si quis fuerit sollicitus consuetudinaliter, mobilis, instabilis, audax, iracundus, calidum cerebrum videtur talis habere, e converso se habens frigiditatem praetendit. Si vero fuerit piger, obliviosus, somnolentus, humidum nimis designat.