sal
passages. It is the softest nerve of the body. (Fig. 136.)

743. The OPTIC NERVE (second pair) passes from the interior of the
cranium, through an opening in the base of the skull, (_fo-ra'men
op'ti-cum_,) to the cavity for the eye. It pierces the coats of the
eye, and expands in the retina.

744. The MOTORES OCULORUM (third pair) pass from the brain, through
an opening of the _sphe'noid_ bone, (_sphe-noid'al fis'sure_,) to the
muscles of the eye.

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739. Describe the arachnoid membrane. 740. What is said respecting the
pia mater? 741. How many pairs of cranial nerves? Name them. 742.
Describe the olfactory nerve. 743. The optic nerve. 744. Describe the
motores oculorum.

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745. The PATHETICUS (fourth pair) passes from the brain, through the
sphenoidal fissure, to the superior oblique muscle of the eye.

[Illustration: Fig. 125. The distribution of the third, fourth, and sixth
pairs of nerves, to the muscles of the eye. 1, The ball of the eye and
rectus externus muscle. 2, The upper jaw. 3, The third pair, distributed
to all the muscles of the eye, except the superior oblique, and external
rectus. 4, The fourth pair passes to the superior oblique muscle. 6, The
sixth pair, is distributed to the external rectus muscle.]

746. The TRIFACIAL NERVE (fifth pair) is analogous to the spinal
nerves in its origin by two roots, from the anterior and posterior
columns of the spinal cord. It has a ganglion, like the spinal nerves
upon its posterior root. For these reasons, it ranges with the spinal
nerves, and is considered the cranial spinal nerve. This nerve divides
into three branches:--The _oph-thal'mic_, superior _max'il-la-ry_, and
inferior _max'il-la-ry_.

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745. The patheticus. What does fig. 125 represent? 746. What is the
trifacial nerve sometimes called? Why is it classed with the cranial
spinal nerves? Give the names of its branches.

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747. The ophthalmic nerve passes from the cranial cavity through the
sphenoidal fissure. It sends branches to the forehead, eye, and nose.
The superior maxillary nerve passes through an opening in the base of
the skull, (_foramen ro-tund'dum_,) and sends branches to the eye, the
teeth of the upper jaw, and the muscles of the face. The inferior
maxillary nerve escapes from the cranial cavity through an opening
called _foramen o-va'le_. It sends branches to the muscle