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THE FIFTH, TRIGEMINAL OR TRIFACIAL NERVE. 637 
sphenoidal fissure, above the muscles of the eyeball, and terminates in the orbital 
(superior) surface of the superior oblique muscle. 
Communications.—In the cavernous sinus the nerve receives (1) a communicating 
branch from the cavernous or carotid plexus on the internal carotid artery, and (2) a 
slender filament from the ophthalmic division of the fifth nerve. 
THE FirrH, TRIGEMINAL OR TRIFACIAL NERVE. 
The trigeminal nerve (n. trigeminus) arises from the surface of the pons Varolii 
in its outer part by two roots, a large sensory root (portio major) and a small motor 
root (portio minor) (Fig. 452, p. 633). 
The two roots proceed forwards in the 
posterior fossa of the base of the skull, 
and piercing the dura mater beneath 
the attachment of the tentorium cere- 
bell to the superior border of the 
petrous portion of the temporal bone, 
enter a cavity in the dura mater 
(cavum Meckelii) over the apex of 
the petrous bone. The large sensory 
root gradually conceals the small 
motor root in its course forwards, 
and expands beneath the dura mater 
into a large flattened ganglion,—the 
Gasserian ganglion (ganglion semi- 
lunare). This ganglion occupies an 
impression on the apex of the petrous 
portion of the temporal bone, and 
from it three large trunks arise— 
the ophthalmic or first, the superior 
maxillary or second, and the inferior 
maxillary or third divisions of the 
nerve. The small motor root of the 
nerve passes forward beneath the 
Gasserian ganglion, and is wholly in- 
corporated with the inferior maxillary val 
division of the nerve. Hy it 
Ophthalmic Division (n. ophthal- | 
micus).—The ophthalmic nerve passes 
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Fic. 458.—DISTRIBUTION OF SENSORY NERVES TO THE 
forwards to the orbit through the Pima ANON NEG: 
middle fossa of the base of the skull, Ophth, Ophthalmic division of the fifth nerve ; St, Supra- 
beneath the dura mater. It lies in the trochlear branch; 8.0, Supra-orbital branch; L.'T, 
outer wall of the cavernous sinus, at Infra-trochlear branch ; UL, Lachrymal branch 3 N, 
l 1 lead fhe ft tl * External nasal branch ; Sup.Max, Superior maxillary 
eo Wwel 2CVe an C_LOurtn Nerve, division; T, Temporal branch; M, Malar branch ; 
and reaches the orbit through the 1.0, Infra-orbital branch ; Inf.Max, Inferior maxillary 
a yerhee io 5 division ; A.T, Auriculo-temporal branch ; B, Buccal 
sphenoidal fissure (Fig. 455). branch ; M, Mental branch ; C2, 3, Branches of the 
In the wall of the cavernous sinus the second and third cervical nerves ; G.O, Great occipital 
ophthalmic nerve gives off (1) a small nerve; §.O, Small occipital nerve } G.A, Great 
= auricular nerve ; 8.C, Superficial cervical nerve ; C3, 
recurrent branch to the dura mater Least occipital nerve; 4, 5, 6, Posterior primary 
(n. tentorii), (2) communicating branches division of 4th, 5th, and 6th cervical nerves. 
to the cavernous plexus of the sym- 
pathetic on the internal carotid artery, and (3) small communicating twigs to the trunks 
of the third, fourth, and sixth nerves. 
In the sphenoidal fissure the nerve divides into three main branches—lachrymal, 
frontal, and nasal (Fig. 459). 
The lachrymal nerve (n. lacrymalis) enters the orbit through the outer 
angle of the sphenoidal fissure, above the orbital muscles. Passing forwards 
beneath the periosteum to the anterior part of the orbit, the nerve ends by 
