794 NERVOUS SYSTEM OF THE HORSE 
part of the thalamus, and (3) the anterior quadrigeminal body (indirectly). The fibers which 
go to the medial geniculate body appear to belong to Gudden’s commissure and to be non-visual 
in function. The visual fibers, which come from the lateral part of the retina of the same side 
and the medial part of the retina of the opposite side, terminate about cells in the anterior quad- 
rigeminal body and the part of the thalamus which corresponds to the pulvinar and lateral genicu- 
late body of man. 
the eyeball, and complete the reflex are. 
From the cells of the former fibers pass to the nuclei of the motor nerves of 
Fibers proceed from the cells of the thalamus to the 
visual area of the cortex in the occipital part of the hemisphere. 
THE OCULOMOTOR NERVE 
The oculomotor nerve (N. oculomotorius) arises by several radicles from the 
basal surface of the cerebral peduncle, a little lateral to the interpeduncular furrow. 
645.—FLoor oF CRANIAL Cavity or Horse, 
Fic. 
The roots of the cranial nerves are shown on the left side 
and are designated by number: J, Anterior cranial fossa; IJ, 
middle cranial fossa; JIZZ, posterior cranial fossa; a, ethmoidal 
fossa; 6, ethmoidal foramen; c, nasal branch of 
ophthalmic artery; d, orbital wing of sphenoid bone; e, optic 
groove; /, hypophyseal fossa; g, spheno-occipital crest; h, h’, con- 
slight elevation repre- 
foramen for 
tour of hypophysis or pituitary body; h”, 
senting dorsum sell#; 7, k, grooves for nerves and cavernous sinus; 
1, depression for piriform lobe of cerebrum; m, groove for middle 
meningeal artery; n, depression for pons; o, foramen lacerum an- 
terius; p, foramen lacerum posterius; qg, incisura carotica; q’, inci- 
sura ovalis; g”, incisura spinosa; r, depression for medulla oblongata; 
s, hypoglossal foramen; ¢, internal acoustic meatus; u, foramen 
magnum; 2, frontal sinus; w, 
xz, section of petrous temporal; y, section of occipital bone; 2, crista 
galli; 1, 1’, 1”, dotted lines indicating position of olfactory strie 
(After Ellenberger-Baum, Top. Anat. d. Pferdes.) 
zygomatic process of temporal bone; 
and tract. 
nerve (Figs. 635, 636). 
It turns sharply outward and for- 
ward, crosses over the cavernous 
sinus, and continues above the 
maxillary nerve and in company 
with the ophthalmic nerve to the 
foramen orbitale. It emerges 
through the foramen with the lat- 
ter nerve and the abducens and 
divides into two branches. The 
dorsal branch is short and divides 
into two twigs which supply the 
rectus dorsalis and levator pal- 
pebre superioris. The ventral 
branch (Figs. 563, 564) is larger 
and much longer. It supplies the 
motor fibers to the ciliary gan- 
glion (which lies directly on this 
branch in the horse) and short 
branches to the rectus medialis 
and rectus ventralis, and con- 
tinues forward on the latter to 
end in the ventral oblique mus- 
cle. 
The deep origin of the fibers of 
the oculomotor nerve is in the oculo- 
motor nucleus, situated in the gray mat- 
ter of the floor of the cerebral aque- 
duct in the region of the anterior cor- 
pora quadrigemina. 
THE TROCHLEAR NERVE 
The trochlear nerve (N. tro- 
chlearis)! is the smallest of the 
cranial nerves. It arises from 
the anterior cerebellar peduncle 
just behind the corpora quadri- 
gemina, curves outward and for- 
ward, pierces the tentorium cere- 
belli, and passes forward along 
the lateral border of the maxillary 
It emerges from the cranium through a small foramen 
1 Formerly termed the nervus patheticus. 
