The =oculomotor nerve= (N. oculomotorius) arises by several radicles
from the basal surface of the cerebral peduncle, a little lateral to the
interpeduncular furrow. It turns sharply outward and forward, crosses
over the cavernous sinus, and continues above the maxillary nerve and in
company with the ophthalmic nerve to the foramen lacerum orbitale. It
emerges through the foramen with the latter nerve and the abducens and
divides into two branches. The =superior branch= is short and divides
into twigs which supply the rectus superior, retractor, and levator
palpebræ superioris. The =inferior branch= (Figs. 438, 439) is larger
and much longer. It supplies the motor fibers to the ciliary ganglion
(which lies directly on this branch in the horse) and short branches to
the rectus internus and rectus inferior, and continues forward on the
latter to end in the inferior oblique muscle.
The deep origin of the fibers of the oculomotor nerve is in the
oculomotor nucleus situated in the gray matter of the floor of the
cerebral aqueduct in the region of the anterior corpora quadrigemina.