534 THE CRANIAL NERVES. 



and are entirely sensory, while the third or inferior maxillary trunk, 

 receivin<2: a considerable' part from the ganglion, has associated ^Yith it 

 also the' whole of the fibres of the motor root, and thus distributes 

 both motor and sensory branches. 



I.— OPHTHALMIC NEEVE, 



The ophthalmic nerve, or first division of the fifth nerve, the smallest 

 of the three offsets from the Gasseriau ganglion, is somewhat flattened, 

 about an inch in length, and is directed ibrwards and upwards to the 

 sphenoidal fissure, where it ends in branches which pass through the 

 orbit to the surface of the head and to the nasal fossai. In the skull it 

 is contained in the process of the dura mater bounding externally the 

 cavernous sinus, and is jomed by filaments from the cavernous plexus 

 of the sympathetic : according to Arnold, it gives recurrent branches 

 to the tentorium cerebelli. It also ft-equently communicates by a con- 

 siderable branch with the fourth nerve. 



Branches. — Near the orbit the ophthalmic nerve furnishes from its 

 inner side the nasal branch, and then divides into the frontal and lach- 

 rymal branches. These branches are transmitted separately thiough 

 the sphenoidal fissure, and are continued through the orbit (after 

 supplying some filaments to the eye and the lachrymal gland) to their 

 final distribution in the nose, the eyelids and the muscles and integu- 

 ment of the forehead. 



Lachrymal branch. — The lachrymal branch is external to the 

 frontal at its origin, and is contained in a separate tube of dura muter. 

 In the orbit it passes along the outer part, above the muscles, to the 

 outer and upper angle of the cavity. Near the lachrymal gland, the 

 nerve has a connecting filament with the orbital branch of the superior 

 maxillary nerve ; and when in close apposition with the gland, it gives 

 many filaments to that body and to the conjunctiva. Finally, the lach- 

 rymal nerve penetrates the palpebral ligament externally, and ends in 

 the upper eyelid, the terminal ramifications being joined by twigs from 

 the facial nerve. 



Varieties. — Turner records a case m which on ono side the laclirymal nervi 

 was absent, and the g-land was supplied by a twig from the orbital orauc-h of 

 the superior maxillary ; on the other side the lachrjTnal was small, and was 

 aupplemented by a branch from the orbital. (Journal of Anat , vol. vi. p. 101.) 



In consequence of the junction which occurs between the ophthalmic crunk of 

 the fifth and the fourth nerve, the lachj-ymal branch sometimes appears to be 

 derived from both these neiwes. Swan considers this the usual condition of the 

 lachrymal nerve. (" A demonstration of the Nerves of the Human Body,"' page 

 36. London, 1834.) 



Frontal branch. — The frontal branch, the largest division of the 

 ophthalmic, lies, like the preceding nerve, above the muscles in the 

 orbit, being situated between the elevator of the upper eyelid and the 

 periosteum. About midway forwards in the orbit, the nerve divides 

 into two branches, supratrochlear and supraorbital. 



a. The siipratrocldear branch (internal frontal) is prolonged to the 

 inner angle of the orbit, close to the point at which the pulley of the 

 upper oblique muscle is fixed to the orbit. Here it gives downwards a 

 filament to connect it with the infratrochlear branch of the nasal nerve, 

 and issues from the cavity l;)etween the orliicular muscle of the lids and 

 the bone. In this position filaments are distributed to the upper eyelid. 



