CHAP. V. Of the Meninges, that is, the two Membranes called Dura Mater and Pia Mater.
* 1.1THe Crassa meninx is one of the first and principal Membranes of the Body; it goes forth by the sutures and holes of the nerves that proceed out of the skull; and it passes forth by the Bone Ethmoides perforated for that purpose, to carry smells to the Brain, and purge it of excrementitious humors. This same Crassa meninx invests the inner coat of the Nose; also it passes forth of the great hole through which the spinal marrow passes, vested with this Crassa meninx, with all the nerves and membranes. For which cause if any membrane in the whole body be hurt, by reason of that continuation which it hath with the Meninges, it straight commu∣nicates the hurt to the head by consent.
* 1.2The Crassa meninx is thicker and harder then all other membranes in the Body; whereupon it hath got the name of the Dura mater; besides also, it begirts, produces, and defends the other membranes.
* 1.3The use of it is to involve all the Brain, and to keep it when it is dilated, that it be not hurt by the hardness of the skull. For the course of nature is such, that it always places some third thing of a middle nature, betwixt two contraries. Also the Crassa meninx yields another commodity, which is, that it carries the veins and arteries, entring the skull for a long space. For they insinu∣ate themselves into that part, where the duplicate or folded Meninges separate the Brain from the Cerebellum, and so from thence they are led by the sides of the Cerebellum, until they come (as it were) to the top thereof; where being united, they insinuate themselves into that other part of the Crassa meninx, where, in like manner being duplicated and doubled, it parts the Brain at the top into the right and left. These united veins run in a direct passage even to the forehead, after the manner of the Sagittal suture; They have called this passage of the mutually infolded veins, the Torcular or Press,* 1.4 because the blood which nourishes the Brain, is pressed and drops from thence by the infinite mouths of these small veins. Therefore also here is another use of the Cras∣sa meninx, to distinguish the Brain by its duplication, being it thrusts it self deep into its Body, in∣to two parts,* 1.5 the fore and hind, and presently to separate the same into the right and left; that one part being hurt, the other may remain safe and sound, performing its duty to the creature, as we see in some that have the Palsey. Columbus observed that this Meninx was double, and verily I have found it true by m own sight.
The other Meninx or Membrane of the Brain, called Pia mater, is most slender interchased with divers veins and arteries, for its own and the brains nourishment and life. This doth not on∣ly involve the Brain, as the Crassa meninx doth, but also more deeply penetrate in the anfractuous passages thereof, that it may every where joyn and bind it to it self, not easily to be drawn from thence, by many small fibers, whereby it descends even to the cavities of the ventricles thereof. Wherefore you must see it absolutely in the site, as we have mentioned, and not pluck it away unless with the substance of the Brain.
* 1.6These membranes when they are hurt or afflicted, cause grievous and most bitter torment and pain; wherefore I dare say, that these membranes are rather the authors of sense, than the Brain it self, because in diseases of the Brain, as in the Lethargy, the part affected is troubled with little or no sense of pain.