= “ ' 
638 THE NERVOUS SYSTEM. 
supplying branches (@) to the lachrymal gland, ()) to the conjunctiva, and (¢) to the 
skin of the outer canthus of the eye. 
The lachrymal nerve communicates in the orbit with the orbital branch of the superior 
maxillary nerve, and on the face, by its terminal branches, with the temporal branches of 
the facial nerve (Fig. 458). 
The frontal nerve (n. frontalis), entering the orbital cavity through the 
sphenoidal fissure, courses forwards above the ocular muscles, and divides at a 
variable point into two branches—a larger supra-orbital and a smaller supra- 
trochlear nerve. The supra-orbital nerve (n. supra-orbitalis) passes directly forwards, 
and leaves the orbit through the supra-orbital groove or foramen to reach the fore- 
head. It gives off the following secondary branches: (1) the principal branches 
(rr. frontales) are distributed to the forehead and scalp, reaching backwards as far as 
the vertex ; (2) small branches 
supply the upper eyelid; and 
(3) twigs are distributed to the 
frontal sinus. On the fore- 
head the supra-orbital nerve 
communicates with the tem- 
poral branches of the facial 
nerve. The  supra-trochlear 
nerve (n. supra-trochlearis) 
courses obliquely forwards and 
inwards over the tendon of 
the superior oblique muscle 
to reach the inner side of the 
supra-orbital arch. Leaving 
the cavity of the orbit, the 
nerve is distributed to the 
skin of the mesial part of the 
Fic. 459.— SCHEME OF THE DisTRIBUTION OF THE OPHTHALMIC forehead, the root of the nose, 
eg and the inner canthus of the 
eye. 
Vs, Trigeminal nerve, afferent root ; Mo, Efferent root ; G.G, Gasserian 
ganglion ; M, Meningeal branch ; I.C, Branch to internal carotid 
artery ; Oph, Ophthalmic nerve ; S.M, Superior maxillary nerve ; ine ie . Shere 
I.M, Inferior maxillary nerve; III, Communication to oculo- t communicates W Mt 1 the mntra- 
motor nerve; IV, To trochlear nerve; VI, To abducent nerve. trochlear branch of tbe nasal 
Frontal nerve ; f.s, Branches to frontal sinus ; 8.0, Supra-orbital perve, -either before or after 
nerve ; S.t, Supra-trochlear nerve ; L, Branches to upper eyelid. 
Nasal nerve; L.G, Long root to lenticular ganglion ; Sy, Root 
from sympathetic (on carotid artery) ; III, Short root from motor The l Px 
oculi nerve ; C, Short ciliary branches ; L.C, Long ciliary nerves; | * we ; OKRA NS (n. te tsiO= 
I.T, Infra-trochlear nerve; E.N, External, and I.N, Internal ciliaris) enters the orbit 
nasal nerves. Lachrymal nerve ; O, Orbital branch of superior through the sphenoidal fissure, 
maxillary nerve; L.Gl, Lachrymal gland; C, Conjunctival apes = Tne ticeclancranl : 
branch ; L, Branch to eyelids and face. veLween the heads 0 le eX- 
ternal rectus muscle, and be- 
tween the two divisions of the third nerve (Fig. 455, p. 635). It crosses the orbital 
cavity obliquely to reach the anterior ethmoidal foramen, lying in its course below the 
superior rectus and superior oblique muscles, and above the optic nerve and internal 
rectus muscle. By the anterior ethmoidal foramen the nerve is transmitted into the 
cranial cavity, where it lies on the cribriform plate of the ethmoid bone. It enters 
the nasal cavity through the nasal fissure, and terminates by dividing into internal 
and external branches. The internal division supplies the mucous membrane over 
the upper and anterior part of the nasal septum (rr. mediales). The external branch, 
after supplying collateral offsets to the outer wall of the nose (ar. laterales), finally 
appears on the face between the nasal bone and lateral cartilage, and supplies 
branches to the skin of the lower part and tip of the nose. 
The branches of the nasal nerve may be divided into three sets, arising (@) in 
the orbit, (b) in the nose, and (¢) on the face. 
In the orbit the branches are given off in three situations—external to, over, 
and internal to the optic nerve. (a) As the nasal nerve lies external to the optic 
nerve, it gives off the long root of the ciliary ganglion (radix longa). (h) As it 
leaving the orbital cavity. 
