FIFTH PAIR OF NERVES. 



281 



guments of the eyebrow and forehead : one 

 of these branches, as described by Meckel, 

 runs outward, through the orbicularis, toward 

 the external canthus, and establishes anasto- 

 moses with filaments of the facial portio dura 

 nerve. The long branches are two, an external 

 and an internal ; of those the external is, for 

 the most part, the larger ; they ascend beneath 

 the frontalis and the frontal aponeurosis, the 

 former inclining outward, the latter inward, as 

 they ascend ; they distribute in their course 

 ramifications to the muscle, and to the deeper 

 structures of the scalp, as well as some- 

 times, according to Meckel, to the pericra- 

 nium, and traversing the frontal aponeurosis, 

 they become subcutaneous, and terminate in 

 the structure and integument of the scalp. The 

 external communicates with the superficial 

 temporal nerves ; the internal with the internal 

 frontal, the supra-trochlear. They are said both 

 to anastomose with the branches of the sub- 

 occipital nerve; but Meckel states that he 

 has pursued them until they have escaped 

 his sight, and yet he could not discover any 

 anastomoses between them and the branches of 

 that nerve. 



2. The nasal nerve is in size the second 

 branch of the first division of the fifth, and arises 

 always separately from the original trunk. Its 

 course is inferior and internal to those of the 

 other two, and hence the nerve is called by 

 some the inferior, by others the internal branch. 

 It is distributed partly to the eye and its appen- 

 dages and partly to the nostril, arid hence it is 

 also called naso-ocular by Soemmerring. The 

 direction of its course is forward and very 

 much inward ; it passes through the foramen 

 lacerum into the orbit ; then traverses that re- 

 gion from without inward toward its internal 

 wall, and having reached it at the foramen or- 

 bitarium internum anterius, it escapes from the 

 orbit through that foramen, and passes into the 

 cranium ; it emerges into the cranium from 

 beneath the margin of the orbitar process of the 

 frontal bone, and crosses the cribriform plate of 

 the ethmoid obliquely forward and inward, 

 contained in a channel in the bone, and in- 

 vested by the dura mater, until it reaches the 

 crista galli ; it then descends from the cranium 

 into the nostril, through the cleft, which exists 

 at either side of the crista galli at the anterior 

 part of the cribriform plate, and having reached 

 the roof of the nostril, it divides into its final 

 branches.* 



The nasal branch is concealed at its origin 

 by the frontal, which is situate external and 

 superior to it. Before its entrance into the orbit 

 it is placed by the outer side of and closely ap- 

 plied to the third nerve. In entering the orbit 



* The nasal is usually described as terminating 

 by dividing within the orbit into two branches, the 

 ethmoidal or internal nasal, and the infra-trochlear or 

 external nasal : the author has preferred considering 

 the former as the continuation of the nerve, be- 

 cause in inferior animals both the nasal is the prin- 

 cipal portion of the first division of the fifth, or 

 alone constitutes it, and it is manifestly prolonged, 

 as such, into the nostril and the beak. See Com- 

 parative Distribution. 



it passes between the two posterior attachments 

 of the external rectus muscle, in company with 

 the third and sixth nerves, external to the 

 former and between its two divisions, and 

 internal and somewhat superior to the latter. 

 In its course across the orbit the nasal nerve 

 passes above the optic nerve, immersed in fat, 

 and accompanied by the ophthalmic artery, 

 being at the same time beneath the levator 

 palpebrs, the superior oblique, and superior 

 rectus muscles, and in crossing the optic 

 nerve, it is placed between it and the last 

 mentioned muscle. Through the foramen or- 

 bitarium the nerve is accompanied by the an- 

 terior ethmoidal artery, and within the cra- 

 nium is situate beneath but not in contact 

 with the olfactory bulb, being separated from 

 it by the dura mater. The course of the nerve 

 from the orbit to the nostril is liable to be 

 modified by the developement of the frontal 

 sinuses ; when they are very large, and extend, 

 as they not unfrequently do, into the orbitar 

 processes of the frontal bone and the horizontal 

 plate of the ethmoid, the nerve may cross to 

 the side of the crista galli without entering the 

 cranium, being contained in a lamella of the 

 ethmoidal bone. The nasal branch, before 

 entering the orbit, receives, according to Bock, 

 J. F. Meckel, and Cloquet, a filament from 

 the sympathetic. The branches which the nasal 

 gives off, are the lenticular, the ciliary, the 

 infra-trochlear, and the nasal. 



The lenticular branch is given off as the nasal 

 enters the orbit, and on the outer side of the 

 optic nerve ; it is a delicate branch, about half 

 an inch long; it first anastomoses with the supe- 

 rior division of the third nerve ; then runs for- 

 ward along the outer side of the optic nerve, 

 and terminates by joining the superior and pos- 

 terior part of the lenticular ganglion. Accord- 

 ing to Bock and Meckel junior, it occasionally 

 gives off a ciliary nerve, and according to 

 Meckel senior it is, in rare instances, derived 

 from the third nerve. To the latter statement, 

 however, the author hesitates to assent : it ap- 

 pears to him, that it should rather be said in 

 such cases to be wanting. 



The ophthalmic, lenticular or ciliary ganglion, 

 according to Cloquet, is of an oblong form 

 its greater length from behind forward; it is 

 one of the smallest ganglia of the body, 

 being, however, variable in size ; its colour is 

 reddish, at times white; it exists constantly in 

 the human subject : it is situate between the 

 external rectus muscle and the optic nerve, laid 

 against the outer side of the nerve, at a little 

 distance from its entrance into the orbit ; its 

 external surface convex, corresponding to the 

 muscle ; its internal, concave, to the nerve ; to 

 its superior posterior angle is attached the len- 

 ticular twig of the nasal branch of the first 

 division of the fifth ; this filament constituting 

 its long root ; to its inferior posterior angle a 

 filament from the inferior division of the third 

 nerve is attached, constituting its short root. 

 To the posterior part of the ganglion are also 

 attached two filaments derived, one from the 

 cavernous ganglion or the carotid plexus ; the 

 other, the constant existence of which has not 



