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THE Description and Use OF THE NERVES.
CHAP. XXI. The first four Pair of Nerves arising within the Skull are described.
THE division or distinction of the Nerves, by reason of their various respects, is wont to be manifold: to wit, as they are either soft or hard, singular or numerous in their beginnings; or that they serve either to the faculty of Sense, or Motion, or to both together. But they are commonly distinguished, That some Nerves arising within the Skull, proceed from the oblong Marrow; and others going out of the joynts of the Vertebrae, are derived from the spinal Marrow. But besides these, another man∣ner of differencing them seems best to us; to wit, That some Nerves, as it were Clients and Servants of the Brain, perform only spontaneous Acts, and others, Mi∣nisters and Servants of the Cerebel, are imployed only about the exercises of the in∣voluntary Function. There will be no need to assign different Essences or Constitu∣tions of Nerves according to these several differences: but rather that there be in∣stituted a particular Cense or Muster of them, and following the order of Nature, that we especially unfold every one of them in the series in which they are disposed in the animal Body.
Among the Nerves arising from the Skull, the smelling Nerves, or those which are commonly called the Mammillary Processes, lead the way; for that they have their rise before all the rest, and are stretched out forward beyond the Brain it self. These Nerves go out of the shanks of the oblong Marrow within the chamfered bodies and chambers of the Optick Nerves; and being endued with a manifest cavity, open into the first Ventricle of the Brain on either side behind the same chamfered bodies; so that the humidity flowing between the folding of the Brain, is carried through these chanels into the mammillary Processes; whether they go farther forward, shall be anon inquired into: Because these Nerves being broad and large, arising near the chamfered bodies, and from thence stretched forward under the Basis of the Brain, their bulk is increased by degrees till they go into the round Processes like Paps, by which either bosom of the Cribrous or Sieve-like Bone is besmeared. Within the Socket of this Bone these Nerves, as yet soft and tender, obtain Coats of the Dura Mater; with which being divided into many fibres and filaments, and passing through the holes of the Sieve-like Bone, they go out of the Skull: from whence being di∣lated or carried forward into the caverns of the Nostrils, and distributed on every side, they are inserted into the Membrane bespreading those Labyrinths.
If we inquire into the nature and use of these parts, without doubt the mammillary