dis 



OPHTHALMIC NEEVK 773 



tributed to the frontal sinus. On the forehead the supra-orbital nerve com- 

 municates with the temporal branches of the facial nerve. 



N. Supratrochlearis. The supra-trochlear nerve courses obliquely forwards 

 and medially above the tendon of the superior oblique muscle to reach the medial 

 side of the supra - orbital arch, where it leaves the cavity of the orbit; it is 

 distributed to the skin of the medial part of the forehead, the root of the nose, and 

 the medial commissure of the eye. 



It communicates with the infra -trochlear branch of the naso- ciliary nerve, either 

 before or after leaving the orbital cavity. 



N. Nasociliaris. The naso-ciliary nerve (O.T. nasal) enters the orbit through 

 the superior orbital fissure, between the heads of the lateral rectus muscle, 

 and between the two divisions of the oculo-motor nerve (Fig. 652, p. 776). 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 medial rectus muscle. The nerve is transmitted, under the name 

 of anterior ethmoidal, through the anterior ethmoidal foramen into the cranial 

 cavity, where it lies embedded in dura mater on the lamina cribrosa of the 

 ethmoid bone. It enters the nasal cavity through the nasal fissure, and termin- 

 ates by dividing into medial and lateral branches. The medial division supplies 

 the mucous membrane over the upper and anterior part of the nasal septum. 

 The lateral branch, after supplying collateral offsets to the lateral wall of the 

 nasal cavity, finally appears on the face as the external nasal nerve 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 naso-ciliary nerve may be divided into three sets, arising 

 (a) in the orbit, (&) in the nose, and (c) on the face. 



In the orbit the branches are given off in three situations lateral to, above, and 

 medial to the optic nerve. (a) As the nerve lies on the lateral side of the 

 optic nerve, it gives off the radix longa ganglii ciliaris (long root of the ciliary 

 ganglion). (&) As it crosses above the optic nerve, nn. ciliares longi (two long ciliary 

 branches) arise, and pass forwards alongside the optic nerve to the eyeball, (c) On 

 the medial side of the optic nerve the n. infratrochlearis (infra -trochlear nerve) 

 arises, a slender branch which courses forwards below the pulley of the superior 

 oblique muscle to the front of the orbit. It ends on the face by supplying 

 the skin of the root of the nose and the eyelids, and communicates either in 



. the orbit or on the face with the supra-trochlear nerve. On the face it also 



i communicates with zygomatic branches of the facial nerve. 



In the nose the rami nasales mediales (medial nasal branches) supply the mucous 



, membrane of the anterior part of the nasal septum ; the rami nasales laterales (lateral 

 nasal branches) supply the anterior part of the lateral wall of the nasal cavity. 



On the face the terminal filaments of the nerve are distributed, as the ramus 

 nasalis externus (external nasal branch), to the skin of the lower half and tip of 

 the nose. The terminal branch communicates with the zygomatic branches of the 

 facial nerve (Fig. 653). 



Ganglion Ciliare. The ciliary ganglion is associated with the naso-ciliary 

 branch of the ophthalmic nerve and with the inferior division of the oculo-motor 

 nerve. It is a small reddish ganglion, placed between the lateral rectus muscle 



1 and the optic nerve, and in front of the ophthalmic artery. Its roots are three 

 in number : (1) sensory or long, derived from the naso-ciliary branch of the 



: ophthalmic nerve; (2) motor or short, derived from the inferior division of the 



. oculo-motor nerve; and (3) sympathetic, a slender filament from the cavernous 

 plexus on the internal carotid artery, which may exist as an independent root 

 or may be incorporated with the long root from the naso-ciliary nerve. The 

 branches from the ganglion are twelve to fifteen nn. ciliares breves (short ciliary 

 nerves), which pass to the eyeball in two groups above and below the optic nerve. 

 They supply the coats of the eyeball, including the iris and ciliary muscles. The 

 circular fibres of the iris and the ciliary muscle are innervated by the third nerve ; 

 the radial fibres of the iris by the sympathetic. 



