FIFTH PAIR OF NERVES. 



289 



names, viz. the recurrent, the pterygoid, the 

 Vidian, the anastomotic, or sy input hie. 



3. The next branch or branches of the su- 

 perior maxillary nerve are the posterior supe- 

 rior dent ul. These arise from the nerve in 

 front of the internal maxillary artery, between 

 it and the back of the antrum, and are sepa- 

 rated from the artery by the spheno-palatine ; 

 they are very irregular as to their number and 

 precise place of origin ; at times there is but 

 one branch, at others there are two or three : 

 they are distributed to the buccinator muscle 

 and the mucous membrane of the posterior 

 lateral part of the mouth, to the roots of the 

 posterior teeth, the membrane of the maxil- 

 lary antrum, and the gum of the upper jaw. 

 When but one branch is present, its sub- 

 divisions supply the place of the others. It 

 descends into the fossa, behind the superior 

 maxillary bone, and before the internal maxil- 

 lary artery, and after a certain way divides 

 into two branches or sets of branches, posterior 

 and anterior. 



The posterior consists of several long slen- 

 der filaments, which continue to descend im- 

 mersed in the fat of the zygomatic fossa, until 

 they reach the surface of the buccinator muscle; 

 they then in part are distributed to it, but in 

 greater number pass between the fibres of the 

 muscle and are lost in the mucous membrane 

 of the mouth. 



The anterior branch descends for some time, 

 until it reaches the back of the maxilla ; it 

 then enters a canal in the bone, within which 

 it is transmitted forward through the wall of 

 the antrum ; after a short way it escapes from 

 the canal and continues its course forward 

 within the wall, between it and the lining 

 membrane, describing a curve convex down- 

 ward ; having reached the front of the antrum 

 it ascends and terminates by joining either the 

 anterior superior dental or a branch of that 

 nerve. 



During its course around the antrum the 

 anterior branch of the nerve gives off down- 

 ward numerous delicate filaments, which de- 

 scend tow r ard the teeth, traverse the structure 

 of the alveolar arch, and in part are distributed 

 to the roots of the posterior superior teeth in 

 a manner analogous to that of the inferior 

 dental nerves : in part they escape inferiorly 

 from the alveolar arch between the sockets of 

 the teeth, and are consumed in the gums. 

 The nerve is also stated to give filaments to the 

 membrane of the maxillary antrum. 



4. Shortly before its escape from the infra- 

 orbital canal, but at a distance somewhat 

 variable from it, the second division of the 

 fifth gives off its next regular branch, the 

 anterior superior dental : this descends, from 

 the infraorbital canal, through one of its own 

 name in the anterior wall of the antrum to- 

 ward the canine tooth ; it next runs inward 

 above the root of that tooth, and then again 

 descends through the perpendicular process 

 of the maxillary bone, until it reaches the floor 

 of the nostril, and is continued inward through 

 the horizontal process of the bone above the 

 roots of the incisor teeth. 



VOL. ir. 



While descending through the wall of the 

 antrum the anterior superior dental nerve 

 either is joined by the termination of the anterior 

 branch of the posterior dental, or it divides into 

 two, one of which inclines outward and joins 

 that branch, the other pursues the course of 

 the nerve. It supplies the anterior teeth of 

 the upper jaw in the same manner as the pos- 

 terior nerve does the posterior teeth ; it also 

 gives at its termination filaments to the mem- 

 brane of the nostril, and one to the naso- 

 palatine ganglion or nerve. 



Besides the regular dental nerves, others at 

 times arise from the second division of the 

 fifth within the infraorbital canal, and take the 

 place of branches of the regular nerves. 



5. The facial branches of the second division 

 of the fifth are from five to seven in number ; 

 they differ from each other in size, and branch 

 off in different directions; they are distin- 

 guished, according to the direction in which 

 they run and their destination, into three sets ; 

 a superior or palpebral, an inferior or labial, 

 and an internal or nasal. 



For the most part there is but one superior 

 or palpebral branch, though sometimes there 

 are two. This branch is destined to supply the 

 lower eyelid, and is denominated the inferior 

 palpebral nerve ; it presents some variety in its 

 mode of origin and its course ; most frequently 

 it does not separate from the trunk till after the 

 latter has escaped from the infraorbital foramen; 

 but in some instances it does so within the in- 

 fraorbital canal, is transmitted through a dis- 

 tinct canal, and escapes into the face through a 

 separate foramen, situate internal to the infra- 

 orbital; it ascends inward toward the lower 

 lid, in front of the inferior margin of the orbit; 

 in its ascent it is situate beneath the orbicularis 

 palpebrarum, to which it gives filaments, which 

 after supplying the muscle become cutaneous, 

 and it is frequently contained in a superficial 

 groove on the superior maxilla ; having reached 

 the lid it divides into two branches, an external 

 and an internal. The external runs outward, 

 through the lid, toward the external angle, 

 supplies its structures on that side, and anasto- 

 moses with filaments of the portio dura, and of 

 the inferior palpebral branches of the lachrymal 

 nerve. The internal ascends in the course of the 

 original nerve toward the internal canthus of 

 the eye, gives a filament to the side of the nose, 

 which communicates with the naso-lobar branch 

 of the nasal nerve, supplies the lower lid at its 

 internal part, is also distributed to the carun- 

 cula and lachrymal sac, and anastomoses with 

 a filament of the inferior branch of the infra- 

 trochlear nerve described in the account of that 

 nerve. It sometimes anastomoses also with 

 the portio dura. 



When there is a second palpebral branch, it 

 takes the place of the external branch of the 

 former, which in such case is denominated the 

 internal inferior palpebral, and the second the 

 external. It perforates the levator labii supe- 

 rioris muscle ; ascends toward the external 

 angle of the eye, beneath the orbicularis palpe- 

 brarum ; and, like the external branch of the 

 inferior palpebral, already described, supplies 



