456 NERVOUS SYSTEM. 



In its whole course it is united to the trochlearis nerve by 

 close cellular membrane, and does not give off any ramifications 

 before it reaches the orbit, with the exception of the filament 

 sent to the trochlearis nerve. While engaged in the sphenoi- 

 dal fissure it divides into three branches; the Nasal, the Lachry- 

 mal, and the Frontal. 



The Nasal branch of the ophthalmic, is between the other 

 two in size. It ascends obliquely above the optic nerve to gain 

 the internal face of the orbit of the eye, and then passes for- 

 wards just below the superior oblique muscle, involved in a 

 quantity of adipose matter. Shortly after its origin the nasal 

 nerve detaches a branch (the ramus ciliaris) which, situated at 

 the external margin of the optic nerve, runs into the ophthalmic 

 or lenticular ganglion, and constitutes the long root; it then 

 sends off one or more filaments, which, without communicating 

 with this ganglion, penetrate into the eyeball, and are amongst 

 the ciliary nerves which have been described. 



The nasal nerve, continuing to pass forward along the inter- 

 nal paries of the orbit, when it reaches the anterior internal or- 

 bitary foramen, detaches through it the internal nasal or eth- 

 moidal branch, which, thus getting into the cavity of the cra- 

 nium, goes along side of the crista galli, and then passes into 

 the nose through the formost hole of the cribriform plate. It 

 then descends along the anterior part of the nose, on the outer 

 side of the Schneiderian membrane, and is spent by ramifi- 

 cations upon the contiguous portions of the latter. Some of 

 its terminating branches reach the tip of the nose and the 

 ala3.* 



The nasal nerve, after this branch is sent off, is frequent- 

 ly called external nasal, or nervus infra-trochlearis. It con- 

 ti'nues to advance along the under margin of the trochlearis 

 muscle and gets to the trochlea, near which it divides into 

 an upper and an under ramuscle; from them filaments proceed 

 to the upper and under eyelids, to the lachrymal sac, the lachry- 

 mal caruncle, the tunica conjunctiva, and the muscles on the 

 root of the nose. These filaments anastomose with the ter- 

 minating branches of the frontal nerve, the facial, and the in- 



* See Nerves of Nose. 



