THE TRIGEMINAL NERVE 



887 



motor and sympathetic filaments from various sources; these filaments are called 

 the roots of the ganglia. 



The Ophthalmic Nerve (n. ophthalmicus) (Figs. 776, 777), or first division of the 

 trigeminal, is a sensory nerve. It supplies branches to the cornea, ciliary body, 

 and iris; to the lacrimal gland and conjunctiva; to the part of the mucous membrane 

 of the nasal cavity; and to the skin of the eyelids, eyebrow, forehead, and nose. 

 It is the smallest of the three divisions of the trigeminal, and arises from the upper 

 part of the Semilunar ganglion as a short, flattened band, about 2.5 cm. long, 

 which passes forward along the lateral wall of the cavernous sinus, below the 

 oculomotor and trochlear nerves; just before entering the orbit, through the supe- 

 rior orbital fissure, it divides into three branches, lacrimal, frontal, and nasociliary. 



The ophthalmic nerve is joined by filaments from the cavernous plexus of the 

 sympathetic, and communicates with the oculomotor, trochlear, and abducent 

 nerves; it gives off a recurrent filament which passes between the layers of the 

 tentorium. 



Internal carotid artery 

 and carotid plexus 



Upper division of 

 oculomotor nerve 



Sensory 

 root 



Motor root 



Lower division of 

 oculomotor nerve 







FIG. 777. Nerves of the orbit, and the ciliary ganglion. Side view. 



The Lacrimal Nerve (n. lacrimalis) is the smallest of the three branches of the 

 ophthalmic. It sometimes receives a filament from the trochlear nerve, but this 

 is possibly derived from the branch which goes from the ophthalmic to the troch- 

 lear nerve. It passes forward in a separate tube of dura mater, and enters the orbit 

 through the narrowest part of the superior orbital fissure. In the orbit it runs 

 along the upper border of the Rectus lateralis, with the lacrimal artery, and com- 

 municates with the zygomatic branch of the maxillary nerve. It enters the lacrimal 

 gland and gives off several filaments, which supply the gland and the conjunctiva. 

 Finally it pierces the orbital septum, and ends in the skin of the upper eyelid, 

 joining with filaments of the facial nerve. The lacrimal nerve is occasionally 

 absent, and its place is then taken by the zygomaticotemporal branch of the max- 

 illary. Sometimes the latter branch is absent, and a continuation of the lacrimal 

 is substituted for it. 



The Frontal Nerve (n. frontalis) is the largest branch of the ophthalmic, and may 

 be regarded, both from its size and direction, as the continuation of the nerve. 

 It enters the orbit through the superior orbital fissure, and runs forward between 

 the Levator palpebrse superioris and the periosteum. Midway between the apex 

 and base of the orbit it divides into two branches, supratrochlear and supraorbital. 



