Trifacial Nerve 61 



The ophthalmic division passes with the third and fourth nerves 

 along the outer wall of the cavernous sinus, and breaks up into frontal, 

 nasal, and lachrymal branches which enter the orbit through the sphe- 

 noidal fissure. 



1^ frontal nerve lies under the middle of the roof of the orbit, and 

 divides into supra-orbital and supra-trochlear branches. The former 

 emerges by the supra-orbital notch, and, ascending beneath the orbicu- 

 laris palpebrarum in two divisions, passes through the occipito-frontalis 

 to supply the scalp, the outer set of filaments reaching back almost to 

 the lambdoid suture. 



In the case of an injury to the trunk of the supra-orbital nerve, I 

 have seen a crop of vesicles on one side of the forehead and even 

 amongst the roots of the hair, just as vesicles occur, after intercostal 

 neuralgia, in the area of distribution of the affected nerve. 



The supra-trochlear nerve escapes, as its name suggests, above the 

 pulley of the superior oblique, and supplies the skin and mucous 

 membrane of the inner end of the upper eye-lid, and the neighbouring 

 part of the forehead. 



The nasal nerve reaches the inner wall of the orbit by passing 

 across the optic nerve, and enters the cranial cavity through the anterior 

 ethmoidal foramen, leaving it again by the slit at the side of the crista 

 galli. Descending in the nose, it gives branches to the front of the 

 septum, to the roof, and to the upper spongy bones ; it finally escapes 

 between the bone and the cartilage to supply the skin near the nostril. 

 In the orbit it gives off the sensory root to the lenticular ganglion, two 

 long ciliary to the ciliary muscle and iris, and the infra-trochlear branch 

 which supplies the skin and mucous membrane near the lachrymal sac. 



The lachrymal nerve runs along the upper border of the external 

 rectus and ends in the lachrymal gland and the upper eyelid. 



The lenticular ganglion lies at the apex of the orbit on the outer 

 side of the optic nerve. Its sensory root conies from the nasal, and its 

 motor from the third nerve ; its sympathetic twigs are from the 

 cavernous plexus. It gives off eight or ten short ciliary nerves which 

 pierce the back of the sclerotic to reach the ciliary muscle and iris. 



Each division of the fifth nerve contains trophic filaments under 

 whose influence the nutrition of the integuments to which the trunk 

 is ultimately distributed is controlled. When the nerve is paralysed, 

 not only is there insensibility in the forehead, eyelids, and in the 

 conjunctiva and nose, in part, but these areas are apt to be the seat of 

 ulcerations ; conjunctivitis and corneitis may also occur, with escape of 

 the aqueous humour and lens, total destruction of the eyeball resulting. 



In cases of intractable neuralgia it may be deemed advisable to try 

 the effect of stretching or of excising a portion of a nerve, but the treat- 

 ment is somewhat speculative ; if each division of the fifth nerve upon 

 the face were affected the operation could hardly succeed, for the cause 

 would then for certain be of central origin. 



