THE LACHRYMAL NERVE. 



235 



I. OPHTHALMIC NERVE. 



The ophthalmic nerve, or first division of the fifth, the smallest of the three 

 offsets from the Gasserian ganglion, is flattened from side to side, and measures 

 about an inch in length. It is directed forwards and upwards in the outer wall of 

 the cavernous sinus, in company with the third and fourth nerves, towards the 

 sphenoidal fissure, where it ends in branches which pass through the orbit to the 

 surface of the head and to the nasal fossa. In its course forwards, the ophthalmic 

 nerve is joined by filaments from the cavernous plexus of the sympathetic. 



BRANCHES. A small recurrent branch (nerrus tentorii) arises from the ophthalmic 

 trunk near the Gasserian ganglion, and, running backwards across the fourth nerve, 

 to which it generally adheres closely for some distance, ramifies between the layers of 

 the ten tori am. 



Farther forwards the ophthalmic nerve gives off three slender offsets which join 

 respectively the third, fourth, and sixth nerves as they enter the orbit. 



The terminal branches resulting from the division of the ophthalmic nerve close 

 to the orbit are the nasal, which is usually the first to arise and springs from the 

 inner and lower part of the trunk, the frontal and the lachrymal. These branches 



Fig. 155. PLAN OF THE OPHTHALMIC NERVE. (GK D. T.) 



The dotted line repi-esents the limit of the orbit, c G, 

 ciliary ganglion, joined behind by the long root, and giving 

 off in front the short ciliary nerves. 



aie transmitted separately through the sphenoidal 

 fissure, and are continued through the orbit (after 

 supplying some filaments to the eyeball and the 

 lachrymal gland) to their final, distribution in 

 the nose, the eyelids and the integument of the 

 forehead. 



Lachrymal nerve. The lachrymal ne"rve 

 (fig. 152, 3) is external to the frontal at its 

 origin, and is contained in a separate sheath of 

 dura mater. In the orbit it passes along the 

 outer part, above the external rectus muscle, to 

 the outer and upper angle of the cavity. Near 

 the lachrymal gland, the nerve has a connecting 

 filament with the temporal branch of the superior 

 maxillary nerve ; and when in close apposition 

 with the gland, it gives many filaments to that 

 body and to the conjunctiva. Finally, the 

 lachrymal nerve penetrates the palpebral fascia 



externally, and ends in the upper eyelid, and the skin in the neighbourhood of the 

 external angular process of the frontal bone, the terminal ramifications being joined 

 by twigs from the facial nerve. 



Varieties. The lachrymal nerve is occasionally smaller than usual, being reinforced by a 

 twi"- from the temporal branch of the superior maxillary, and it has been seen replaced 

 entirely by an offset of the latter nerve (Turner, Hyrtl). On the other hand, the lachrymal 

 nerve has been found sending an offset through the malar bone in the place of the temporal 

 branch of the superior maxillary nerve, which was absent (G. D. T.). 



The lachrymal branch sometimes appears to be derived in part from the fourth nerve, but 

 in such cases" the additional root is probably composed of fibres that have passed over from 

 the ophthalmic to the fourth, while these nerves are contained in the outer wall of the 

 cavernous sinus. 



