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 336 brain, through an opening of the sphe´noid bone, (sphe-noid´al fis´sure,) to the muscles of the eye.
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.
745. The PATHETICUS (fourth pair) passes from the brain, through the sphenoidal fissure, to the superior oblique muscle of the eye.
Fig. 125.
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.
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.