798 



THE NERVOUS SYSTEM. 



The Lachrymal is the smallest of the three branches of the ophthalmic. Not 

 (infrequently it arises by two filaments, one from the ophthalmic, the other from 

 the fourth. It passes forward in a separate tube of dura mater and enters the 



Internal carotid artery 

 and carotid plexus, 



Sensory 

 root. 



Motor root: 



FIG. 481. Nerves of the orbit and ophthalmic ganglion. Side view. 



orbit through the narrowest part of the sphenoidal fissure. In the orbit it runs 

 along the upper border of the External rectus muscle with the lachrymal artery, 

 and sends off a recurrent branch which joins the orbital branch of the superior 

 maxillary nerve, and occasionally takes the place of the temporal branch of this 

 nerve, which is then absent. Within the lachrymal gland it gives off several 

 filaments, which supply the gland and the conjunctiva. Finally, it pierces the 

 tarsal ligaments, and terminates in the integument of the upper eyelid, joining 

 with filaments of the facial nerve. 



The Frontal is the largest division of the ophthalmic, and may be regarded, 

 both from its size and direction, as the continuation of the nerve. It enters the 

 orbit above the muscles through the highest and broadest part of the sphenoidal 

 fissure, and runs forward along the middle line, between the Levator palpebne 

 and the periosteum. Midway between the apex and 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, and ascends beneath the Corrugator 

 supercilii and Occipito-frontalis muscles, and supplies the integument of the lower 

 part of the forehead on either side of the middle line. 



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 pericrttm'nl 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 



