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_. In the upper and hinder-part of the Hole, from whence the lateral _Sinus's_ issue forth, is to be seen an opening in the Extremity of a _Ductus_, the Mouth whereof lies behind the _Condyli_, which are on the sides of the Occipital Trunk: This _Ductus_ is extended about the length of two Hairs breadth in the Bone, and the Canal enclos'd therein is open'd immediately into the _Vertebral Sinus_: So that one might affirm it to be as it were its Original Source. Whence it appears that the Blood contained in the lateral _Sinus's_ is emptied thro' two places; the greater Portion thereof descending in the _Jugulars_ {90} from the Neck, and the other in the _Vertebral Sinus's_: Sometimes those _Ductus's_ are four only on one side, another while both are stopt up, and the Blood contain'd in the lateral _Sinus's_ is discharg'd into the _Internal Jugulars_. Behind the _Apophysis Mastoides_ on each side is a remarkable Hole, thro' which passeth a thick Vein, which brings back part of the Blood that hath been distributed to the Teguments and Muscles, which cover part of the _Occiput_ or hinder-side of the Head: This Vein is open'd into the lateral _Sinus's_ at the place where they begin to turn about. But in the Heads of some Persons, this Hole is found only on one side, and even sometimes not at all, in which case the Blood contain'd in the Vessels falls into the _External Jugulars_, with which the Branches of this Vein have a Communication. In each _Parietal_ Bone on the side of the _Sagittal_ Suture, at a little distance from the _Lambdoidal_, appears a Hole, thro' which passeth a Vein, that brings back the Blood of the Teguments of the Head, and dischargeth it self into the upper _Longitudinal Sinus_. These Holes are sometimes on both; and then the Blood contain'd in the Branches of this Vein runs into the _External Jugulars_. In the middle of the _Sella_ of the _Os Sphenoides_, we may observe one or two small Holes thro' which (according to the Opinion of some Modern Anatomists) the _Lympha_ contain'd in the _Glandula Pituitaria_ is thrown {91} into the _Sinus_ of the edge of the _Os Sphenoides_; nevertheless it is certain, that these Holes are fill'd only with Sanguinary Vessels, which carry and bring back the Blood of the Bones and Membranes, whereof those _Sinus's_ are compos'd; besides that, these Holes are rarely found in adult Persons.