752 THE NERVOUS SYSTEM 



branch of the nasal nerve and turns upwards on the forehead, accompanied by the 

 frontal artery. It is much smaller than the supraorliital nerve, and it is distributed 

 to a small area of integument around the glabella. It gives twigs to the inner part 

 of the upper evelid. 



(4) Tbe lachrymal nerve is the smallest of the three branches of the ophthalmic 

 division. It passes through the sphenoidal tlssure external to and slightly below 

 the frontal nerve, and is directed forwards and outwards along the ujjper border of 

 the external rectus muscle to the lachrymal gland. Immediately behind the 

 lachrymal gland it communicates with the temporal branch of the orbital nerve, 

 forming a loop convex forwards; from this loop and from the adjacent part of thi' 

 trunk of the nerve a number of twigs pass into the gland substance. A small twig 

 passes beyond the gland and is distributed to the integument and conjunctiva at 

 the outer canthus of the eye. 



(5) The nasal nerve enters the orbit by passing forwards between the superior 

 and inferior divisions of the third nerve, and takes an oblique course forwards and 

 inwards to reach the inner wall of the orbit. In this course it passes between the 

 optic nerve and the superior rectus muscle. It then passes between the superior 

 oblique and the internal rectus, traverses the anterior internal orbital canal, 

 accompanied by the anterior ethmoidal vessels, enters the anterior fossa of the 

 skull, crosses the cribriform plate of the ethmoid l)one under cover of the dura 

 mater, and enters the nasal fossa through a slit-like aperture at the side of the crista 

 galli (the ethmoidal fissure). It terminates within the nasal fossa by dividing into 

 three branches: an internal, or septal; an external; and an anterior, or 

 terminal. 



Branches. — The long root to the lenticular ganglion is given off at the 

 sphenoidal fissure. It is a slender filament which passes forwards to join the upper 

 and back part of the ganglion. The long ciliary nerves, usually two in number, 

 arise from the nasal trunk as the latter is crossing the optic nerve. They are 

 directed forwards along the inner side of the optic nei-ve, and join the lower set of 

 short ciliarv nerves after they pierce the sclerotic (page 851). The infratrochlear 

 nerve is given off by the nasal just before the latter enters the anterior internal 

 orbital canal. It passes forwards beneath the j^ulley of the superior oblique muscle, 

 and supplies the skin and conjunctiva around the inner canthus of the eye and 

 the integument of the upper part of the nose. It also supplies the lachrymal sac 

 and caruncle. It communicates with the supratrochlear nerve in front of (some- 

 times behind) the pulley. 



The internal or septal branch of the nasal nerve runs downwards and for- 

 wards on the upper and front part of the nasal septum. 



The external branch gives tw^o or three twigs- to the anterior extremities of the 

 superior and middle turbinated bones, and to the mucous membrane of the outer 

 wall of the nose. 



The terminal or anterior branch runs downwards in a groove on the inner 

 surface of the nasal bone. It pierces the wall of the nose Ijetween the nasal bone 

 and the lateral cartilage, and supplies the integument of the lower part of the 

 dorsum of the nose as far as the tip of that organ. 



Lenticular Ganglion 



The lenticular, ciliary, <>r ophthalmic ganglion is a small reddish-grey body 

 about the size of a pin's head. It is (luadrilateral in outline, and its outer and 

 inner surfaces are slightly convex. It is ])laced between the optic nerve and the 

 external rectus muscle, about a quarter of an inch in front of the sphenoidal fissure. 

 Following the general rule applying to the sporadic ganglia which are connected 

 witli the fifth nerve, it is ])rovided Avith three roots, a motor, a sensory, and a 

 sympathetic. The motor or short root is derived from the branch of the oculo- 

 motor to the inferior oblique muscle; it enters the posterior inferior angle of the 

 ganglion. The sensory or long root is a branch of the nasal nerve; it passes 

 along the outer side of tbe o})tic nerve, and enters the U})})er and back part of the 

 ganglion. Tbe sympathetic root is derived from tlie cavernous plexus of the 

 sympathetic; it may enter tlie ])ack \m\y{ of the ganglion in tlie form of tine tAvigs, 



