FIFTH PAIR.-OPHTHALMIC NERVE. 597 



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

 receiving a considerable part from the ganglion, has associated with it also 

 the whole of the fibres of the motor root, and thus distributes both motor 

 and sensory branches. 



OPHTHALMIC NERVE. 



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

 the three offsets from the Gasserian ganglion, is somewhat flattened, about an 

 inch in length, and is directed forwards and upwards to the spheuoidal 

 fissure, where it ends in branches which pass through the orbit to the sur- 

 face of the head and to the nasal fossse. In the skull it is contained in the 

 process of the dura mater bounding externally the cavernous sinus, and is 

 joined by filaments from the cavernous plexus of the sympathetic : according 

 to Arnold, it gives recurrent branches to the tentorium cerebelli. It also 

 frequently communicates by a considerable branch with the fourth nerve. 



Near the orbit the ophthalmic nerve furnishes from its inner side the 

 nasal branch, and then divides into the frontal and lachrymal branches. 

 These branches are transmitted separately through 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 integument of the forehead. 



LACHRYMAL BRANCH. 



The lachrymal branch is external to the frontal at its origin, and is con- 

 tained in a separate tube of dura mater. 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 lachrymal nerve penetrates the palpebral ligament externally, and ends 

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

 the facial nerve. 



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

 fifth and the fourth nerve, the lachrymal branch sometimes appears to be derived 

 from both these nerves. 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 supra- 

 orbital. 



a. The supratrochlear 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 between the orbicular muscle of the lids and the bone. In this position 

 filaments are distributed to the upper eyelid. The nerve next pierces the 



