282 



FIFTH PAIR OF NERVES. 



been yet established, from the spheno-palatine 

 ganglion. 



The ganglion gives off from its anterior ex- 

 tremity a considerable number of very delicate 

 filaments, denominated from their distribution 

 ciliary : they amount to from twelve to sixteen ; 

 are reddish and tortuous; and run forward 

 along the optic nerve to the back of the eye, 

 which they enter at a short distance from the 

 nerve. They are distinguished into two fasci- 

 culi, superior and inferior ; which are attached, 

 one to the superior anterior, the other to the 

 inferior anterior angles of the ganglion : the 

 former is the smaller ; contains at first but three 

 filaments, which, as they proceed, divide so as 

 to produce six, and run parallel to each other 

 above the optic nerve : the second fasciculus is 

 situate on the outside of and beneath the optic 

 nerve, and contains from six to ten filaments col- 

 lected at their origin into six branches: they pass 

 beneath the nerve and incline inward, so as 

 to gain, some of them, its inner side : one of 

 them runs outward and joins one of the ciliary 

 branches of the nasal nerve. The ciliary nerves 

 all penetrate the sclerotic coat of the eye sepa- 

 rately and obliquely ; then run forward between 

 the sclerotic and choroid coats, without giving 

 filaments to either, lodged in channels upon 

 the inner surface of the former: as they ap- 

 proach the ciliary circle they divide, each into 

 two or three filaments, which enter the circle 

 and are lost in it : some of them pierce the 

 choroid at the anterior part of the eye, and go 

 to the ciliary processes. 



The ciliary branches are two or three in 

 number ; they are very delicate, and are given 

 off, while the nasal is crossing the optic nerve ; 

 they run forward along the optic, imbedded in 

 fat, penetrate the sclerotic coat of the eye pos- 

 teriorly, and then continue forward between 

 the sclerotic and choroid coats, in like manner 

 as the other ciliary nerves, to the ciliary circle. 



The infra-trochlear branch, so called by the 

 elder Meckel, because it escapes from the 

 orbit beneath the trochlea of the oblique mus- 

 cle, is also called external nasal. It is given 

 off when the nasal has reached the inner wall 

 of the orbit, and as it is about to enter the fora- 

 men orbitarium ; it is a branch comparatively 

 considerable, at times longer, at others smaller 

 decidedly than the continuation of the nasal ; 

 it runs directly forward along the inner wall, 

 beneath the superior oblique muscle, toward 

 its trochlea, and having reached that, escapes 

 from the orbit beneath it. It then divides, in 

 the internal can thus of the eye, into two 

 branches, a superior and an inferior. 



The infra-trochlear, while within the orbit, 

 gives off occasionally, soon after its origin, 

 a small branch, which returns and joins the 

 nasal before it enters the foramen orbitarium ;* 

 also a delicate branch, which joins a corre- 

 sponding branch given off either by the supra- 

 trochlear or the frontal. The distribution of the 

 nerve resulting from their junction has been 

 already described under the frontal nerve. Of 

 its ultimate branches, the superior joins and 



forms a plexus with a branch of the supra-ti'o- 

 chlear nerve, already described, given off either 

 immediately before or after that nerve has 

 escaped from the orbit. From the junction of 

 the two, numerous delicate ramifications are 

 distributed to the upper eyelid and to the eye- 

 brow. The inferiorgives off several ramifications, 

 which are distributed to the origin of the cor- 

 rugator, the orbicularis, and the pyramidalis 

 nasi muscles ; to the conjunctiva, at the inter- 

 nal canthus ; the carunculalachrymalis and the 

 lachrymal sac. Of those ramifications, one de- 

 scends before the tendon of the orbicularis, and 

 communicates with a branch of the portio 

 dura: another communicates with a branch of 

 the infra-orbital ; but the latter anastomosis is 

 uncertain.* 



The nasal nerve having entered the nostril di- 

 vides at the roof of the cavity into two branches, 

 an external and an internal: of these the former 

 descends behind the nasal process of the frontal 

 and the corresponding nasal bones, contained 

 in the groove or canal observable upon their 

 posterior surface. It escapes from beneath 

 them at their inferior margin, emerging between 

 it and the lateral cartilage of the nose, and then 

 descends along the corresponding ala, superfi- 

 cial to the cartilage, and covered by the mus- 

 cles of the ala, toward the tip : as it approaches 

 the tip, it divides into two filaments, one of 

 which is distributed to that part, and the other 

 to the ala. During its descent along the side 

 of the nose it also gives off some delicate fila- 

 ments, and anastomoses with the ramifications 

 of the nasal branches of the infra-orbital nerve 

 and with the portio dura. It is called by 

 Chaussier the naso-lobar : it is also generally 

 known as the nerve of Cotunnius. The second 

 branch, as it proceeds, divides presently into 

 two, of which one attaches itself to the septum, 

 and descends, between the pituitary membrane 

 and the periosteum, parallel and near to its an- 

 terior margin, as the naso-palatine of Scarpa 

 does to its posterior : as it proceeds, it furnishes 

 ramifications to the membrane of the septum. 

 The second attaches itself to the outer wall of 

 the nostril, and descends, in like manner be- 

 tween the mucous membrane and the perios- 

 teum, along its anterior part, in front of the 

 middle turbinate bone, until it reaches the an- 

 terior extremity of the inferior one : it then 

 breaks up into branches, of which some are 

 distributed to the convex surface of the latter 

 bone in front, and others beneath it to the an- 

 terior part of the inferior meatus. The distri- 

 bution of the branch is very happily represented 

 in Arnold's Icones. 



The nasal nerve is described as giving also, 

 in some instances, but not uniformly, a branch 

 to the membrane of the superior turbinate 

 bone, at the superior part of the nostril. 



3. The third branch of the first division of the 

 fifth is the lachrymal: it has been so called by 

 Winslow from its distribution to the lachrymal 

 gland : it is the smallest of the three branches : 

 its course is external to that of the others, and 

 hence it is also called the external branch. It 



* J. F. Mcckcl. 



* The elder Meckel. 



