THE TRIGEMINAL NERVE. 



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margin of the Gasserian ganglion, the formation of the mandibular nerve being com- 

 pleted by the accession of the motor'root of the trigeminal. 



I. The Ophthalmic Nerve. — The ophthalmic nerve (n. ophthalmicus) (Fig. 

 1056), the smallest of the three divisions, is purely sensory and supplies the upper 

 eyelid, the conjunctiva, the eyeball, the lachrymal gland, caruncle and sac, the fore- 

 head and anterior part of the scalp, the frontal sinus and the root and anterior por- 

 tion of the nose. It arises from the anterior margin of the Gasserian ganglion and 

 passes upward and forward for about 25 mm. in the external wall of the cavernous 

 sinus, lying below the fourth nerve. Reaching the sphenoidal fissure it breaks up 

 into its terminal branches, which pass through the fissure into the orbit. 



Branches and Distribution. — The branches of the ophthalmic nerve are: 

 (i) the. reair rent, (2) the covnnunicating, (3) the lachrymal, (4) \.\\^ frontal, and 

 (5) the nasal, of which the last three are terminal branches. 



Fig. 1056. 



Supratochlear nen-e 

 Nasal nerve 



Olfactorj' bulbs 



superior oblique muscle 

 IV. nerve 



Cut edge of bone 

 Optic nerve 



Optic chiasm 

 internal carotid arterj' 



Optic tract 

 VI. nerve 



III. nerves 

 Cerebral peduncles 



■Supraorbital nerve 

 Lachrymal gland 



Le%'ator palpebrce superions 

 ■; — Superior rectus 



Frontal nerve 

 External rectus 



Lachrymal nerve 



Ophthalmic division of V. nerve 

 Maxillary division of V. nerve 

 Mandibular division of V. uerve 



Gasserian ganglion 



Meatus auditorius internus 



VII. nerve, motor part 

 Pars intermedia 



VIII. nerve 



Roof of right orbit has been removed to expose branches of ophthalmic division of trigeminal nerve; Gasserian 

 ganglion, and third, fourth, sixth, seventh and eighth nerves also seen. 



1. The recurrent branch (n. tentorii.) arises shortly after the nerve leaves the 

 ganglion. It passes across and is adherent to the trochlear nerve and is distributed 

 between the layers of the tentorium cerebelli. 



2. The communicating branches are three slender filaments which are given 

 of! before the nerve breaks up into its terminal branches ; they join the trunks of the 

 third, fourth and sixth nerves, to whose muscles they supply sensory fibres. During 

 its passage through the cavernous sinus, the ophthalmic nerve receives some tiny^ 

 filaments from the cavernous sympathetic plexus. 



3. The lachrymal nerve (n. lacrimalis) (Fig. 1053) is the smallest of the 

 terminal branches. It lies to the outer side of the frontal nerve and traverses the 

 outer angle of the sphenoidal fissure in its own sheath of dura mater. It passes 

 above the origin of the orbital muscles and courses along the lateral wall of the orbit, 

 above the external rectus, to the upper outer angle of the orbit, where it pierces the 

 palpebral fascia near the external canthus to terminate in the upper eyelid. It sup- 

 plies the lachrymal gland, the upper eyelid and the skin around the external canthus, 



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