THE BRANCHES OF THE FIFTH NERVE. 



727 



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

 supra-orbital. 



The supratrochlear branch, the smaller of the two, passes inward, above the 

 pulley of the superior oblique muscle, and gives off a descending filament, which 

 joins with the infratrochlear branch of the nasal nerve. It then escapes from the 

 orbit between the pulley of the Superior oblique and the supra-orbital foramen, 

 curves up on to the forehead close to the bone, ascends beneath the Corrugator 

 supercilii and Occipito-frontalis muscles, and, dividing into branches which pierce 

 these muscles, it supplies the integument of the lower part of the forehead on 

 either side of the middle line and sends filaments to the conjunctiva and skin of 

 the upper lid. 



Interned carotid artery 

 and carotid plexus. 



Sensory 

 root. 



Motor root: 



FIG. 393. Nerves of the orbit and ophthalmic ganglion. Side view. 



The supra-orbital branch passes forward through the supra-orbital foramen, 

 and gives off, in this situation, palpebral filaments to the upper eyelid. It then 

 ascends upon the forehead, and terminates in cutaneous and pericranial branches. 

 The cutaneous branches, two in number, an inner and an outer, supply the 

 integument of the cranium as far back as the occiput. They are at first situated 

 beneath the Occipito-frontalis, the inner branch perforating the frontal portion of 

 the muscle, the outer branch its tendinous aponeurosis. The pericranial branches 

 are distributed to the pericranium over the frontal and parietal bones. 



The Nasal nerve is intermediate in size between the frontal and lachrymal, and 

 more deeply placed than the other branches of the ophthalmic. It enters the orbit 

 between the two heads of the External rectus, and passes obliquely inward across 

 the optic nerve, beneath the Superior rectus and Superior oblique muscles, to the 

 inner wall of the orbit, where it passes through the anterior ethmoidal foramen, 

 and, entering the cavity of the cranium, traverses a shallow groove on the front of 

 the cribriform plate of the ethmoid bone, and passes down, through the slit by the 

 side of the crista galli, into the nose, where it divides into two branches, an inter- 

 nal and an external. The internal branch supplies the mucous membrane near 

 the fore part of the septum of the nose. The external branch descends in a groove 

 on the inner surface of the nasal bone, and supplies a few filaments to the mucous 

 membrane covering the fore part of the outer wall of the nares as far as the infe- 

 rior spongy bone ; it then leaves the cavity of the nose, between the lower border 

 of the nasal bone and the upper lateral cartilage of the nose, and, passing down 

 beneath the Compressor nasi, supplies the integument of the ala and the tip of the 

 nose, joining with the facial nerve. 



