In the Os Sphenoides, or Wedge-like Bone, behind the Hole thro' which passeth the hindermost Fibre of the fifth Pair of Nerves lies another small Hole, almost round, that gives Entrance to a Branch of the External Carotick Artery, which in entring, immediately adheres to the Dura Mater, and forms many Ramifications to overspread the whole Portion of this Membrane, which covers the sides, and the upper-part of the Brain.
At the bottom and top of the lateral outward part of the Orbit of the Eye, above the acute Angle, for want of the Os Sphenoides, there is a Hole thro' which passeth an Artery, being a Twig of a Branch of the Internal Carotick, which is diffus'd in the Eye, and distributed to almost the whole Portion of the Dura Mater, that covers the fore-part of the Brain.
The Vertebral Artery in entring into the Skull, furnisheth it on each side with a considerable Branch, which is dispers'd throughout the whole Portion of the Dura Mater that covers the Cerebellum.
As for the Veins that accompany these Arteries, they almost all go out of the Skull thro' the same Holes where the other enters.
There are four thick Arteries which convey to the Brain the Matter with which it is nourish'd, and that whereof the Spirits are form'd, viz. the two Internal Caroticks, and the two Vertebrals.
The Internal Carotick Arteries enter into the Skull thro a particular Ductus made in the Temporal Bone, the Mouth thereof being of an Oval Figure and situated in the outward part of the Basis of the Skull, before the Hole of the Internal Jugular. This Ductus extends it self obliquely from the back-side forward, and after having made about three Hairs breadth in length, is terminated in the hinder-part of the Os Sphenoides. The Artery traverseth the whole winding Compass of this Ductus, which resembles the Figure of the Roman Letter S, and at the Mouth of the same Ductus runs under the Dura Mater along the sides of the Os Sphenoides to the Anterior Apophyses Clinoides, where it riseth up again, to perforate the Dura Mater, and to adhere to the Root of the Brain. These Vessels, in like manner, after their departure from the Bone of the Temples to the place where they pierce the Dura Mater, make a second Circuit in form of the Roman Character S. At the place where these Carotick Arteries penetrate the Dura Mater, they send forth a thick Branch, which enters into the Orbit of the Eye, by the lower-part of the Hole, thro' which the Optick Nerve hath its Passage.
The Vertebral Arteries proceeding from the Holes of the transverse Apophyses of the first Vertebra, turn about in passing under the upper oblique Apophyses of the seven Vertebra's: Afterward they perforate the Dura Mater, and running under the Marrow, enter into the Skull thro' the Occipital Hole; then inclining one toward another, they are re-united, and form only one single Trunk.
The Veins that bring back the Blood from the Substance of the Brain, are emptied into the Sinus's of the Dura Mater, which are all discharg'd into those that are call'd Lateral, which last go out of the Skull immediately under the Nerves of the eighth Pair, thro' the hinder-part of the Hole made by the meeting of the Occipital Bone, and the Apophysis Petrosa. These Lateral Sinus's fall into the Internal Jugulars, which are receiv'd into a considerable Sinking hollow'd on each side in the outward, part of the Basis of the Skull, which is nam'd the Pit or Hole of the Internal Jugular.