_An exact Historical Account of all the Holes of the Skull, and the Vessels that pass thro' them._ To attain to an exact Knowledge of all the Holes with which the inside of the _Basis_ of the Skull is perforated, they are to be consider'd either with respect to the Nerves, or to the Sanguinary Vessels. {84} There are nine Pairs of Nerves that arise from the _Medulla Oblongata_, and go forth out of the Skull through many Holes hereafter nam'd. The first Pair is that of the _Olfactory_ Nerves, appropriated to the Sense of Smelling, which are divided below the _Os Cribiforme_, or Sieve-like Bone, into divers Threads, that passing into the Nose through many Holes with which this Bone is pierc'd, are distributed to the inner Tunick of the Nose. The second Pair is that of the _Optick_ or Visual Nerves, that pass into the Orbits of the Eyes, thro' certain peculiar Holes made in the _Os Sphenoides_, or Wedge-like Bone, immediately above the _Anterior Apophysis Clinoides_. In the Portion of the _Os Sphenoides_, that makes the _Basis_ of the Orbit, lies a Fissure about seven or eight Hairs breadth long, which is to be observ'd chiefly at the bottom, that is to say, below the Hole, thro' which the Optick Nerve passeth; where it is almost round, and larger than at the top, where it is terminated in a very long and acute Angle. There are many Pairs of Nerves that enter into the Orbit thro' this Fissure, _viz._ 1. The third Pair, call'd the _Motorii Oculorum_. 2. The fourth Pair, nam'd _Pathetici_, by Dr. _Willis_. And 3. The whole sixth Pair. Besides these three Pairs, which go entire thro' this Cleft, there is also a Passage for the upper Branch of the foremost Fibre of the fifth Pair, which the same renowned Physician calls the _Ophthalmick_ Branch. Beyond the lower-part of the said Fissure, toward the hinder-part of the Head, is to be seen {85} in the _Os Sphenoides_ on each side, a Hole that doth not penetrate the _Basis_ of the Skull, but makes a kind of _Ductus_, about an Hair's breadth long, which is open'd behind the Orbit on the top of the Space between the _Apophysis Pterygoides_, and the third Bone of the Jaw; thro' this _Ductus_ runs the lower Branch of the foremost Fibre of the fifth Pair. About the length of two Hairs breadth beyond these _Ductus's_, we may also discover in the _Os Sphenoides_, or Wedge-like Bone, two Holes of an Oblong and almost Oval Figure, which are plac'd in the hindermost sides of that of the _Os Sphenoides_, and gives passage to the hindermost Fibre of the fifth Pair.