966 THE NERVOUS SYSTEM 



(c) TheNaso-ciliary (nasal) Nerve enters the orbit between the two heads of the 

 rectus lateralis and between the upper and lower divisions of the oculomotor nerve. In 

 the orbit it lies at first on the outer side of the optic nerve, but, as it runs obliquely for- 

 wards and inwards to the inner wall of the orbital cavity, it crosses above the optic 

 nerve and between it and the red us superior, and near t he border of the rectus medi- 

 alis it divides into its two terminal branches, the infratrochlear and anterior ethmoid 

 (fig. 701). 



Its several branches are: (i) The long root of the ciliary ganglion which is 

 given off at the superior orbital (sphenoidal) fissure. It is a slender filament which 

 runs forwards on the outer side of the optic nerve to the upper and back part of the 

 ganglion (fig. 701). 



(ii) The long ciliary nerves, usually two in number, which arise from the naso- 

 ciliary nerve as the latter is crossing above the optic nerve. They run forwards, on 

 the inner side of the optic nerve, pierce the sclerotic, and are distributed with the 

 lower set of short ciliary nerves (fig. 701). 



(iii) The posterior ethmoidal (spheno-ethmoidal) branch springs from the 

 posterior border of the naso-ciliary nerve near the upper border of the rectus medialis. 

 It passes through the posterior ethmoidal canal and is distributed to the mucous 

 membrane of the posterior ethmoidal cells and the sphenoidal sinus. 



(iv) The infratrochlear nerve passes forwards between the obliquus superior and 

 the rectus medialis, and under the pulley of the former muscle divides into two 

 branches: The superior palpebral branch helps to supply the eyelids and usually 

 anastomoses with the supratrochlear nerve. The inferior palpebral branch is 

 distributed to the lachrymal sac, the conjunctiva and skin of the inner part of 

 the upper eyelid, the caruncle, and the skin of the upper part of the side of the 

 nose. 



(v) The anterior ethmoidal (distal part of the nasal) nerve, passing forwards 

 and inwards between the obliquus superior and the rectus medialis, leaves the orbit 

 through the anterior ethmoidal foramen, accompanied by the anterior ethmoidal 

 vessels, and enters into the anterior fossa of the cranium (fig. 701). It then crosses 

 the lamina cribrosa of the ethmoid, lying outside the dura mater, which separates 

 it from the olfactory bulb, and descends into the nasal fossa through the ethmoidal 

 fissure, a slit-like aperture at the side of the crista galli. In the nasal fossa it ter- 

 minates by dividing into two sets of anterior nasal branches: the internal nasal 

 branches and the external nasal branch (fig. 699). 



The internal nasal branches divide into the medial nasal branches (the 

 septal branches of the nasal nerve) , which run downwards and forwards on the upper 

 and front part of the septum, and the lateral nasal branches (the external terminal 

 branch of the nasal nerve), which give twigs to the anterior extremities of the supe- 

 rior and middle nasal conchse (turbinated bones), and to the mucous membrane of the 

 lateral wall of the 'nose (fig. 699) . 



The external nasal branch (the anterior terminal branch of the nasal nerve) 

 runs downwards in a groove on the inner surface of the nasal bone. It pierces the 

 wall of the nose between the nasal bone and the upper lateral cartilage, and supplies 

 the integument of the lower part of the dorsum of the nose as far as the tip. 



(2) THE MAXILLARY NERVE OR SECOND DIVISION OF THE TRIGEMINDS 



The maxillarj' nerve is entirely sensory in function and it is intermediate in size 

 between the ophthalmic and mandibular nerves. 



It springs from the middle of the anterior border of the semilunar (dasserian) 

 ganglion and runs forwards in the lower and outer part of the lateral wall of the 

 cavernous sinus (fig. 702). Leaving the middle fossa of the cranium, by passing 

 through the foramen rotundum, it enters the ptery go-palatine (.spheno-maxillary) fossa 

 (fig. 707), where it is connected with the spheno-palatine ganglion; then, changing its 

 name, it passes forwards, as the infra-orbital nerve, through the inferior orbital 

 (spheno-maxillary) fissure into the infra-orbital sulcus in the floor of the orbit : con- 

 tinuing forwards it traverses the infra-orbital canal accompanied by the infra-orbital 

 artery, and appears in the face, beneath the quadratus (levator) labii superioris and 

 above the caninus (levator anguli oris), where it divides into four sets of terminal 

 branches which anastomose more or less freely with branches of the facial nerve to 

 form the infra-orbital plexus. 



