754 THE NERVOUS SYSTEM 



superior dental nerves constitute the tliiid set. (4) The terminal branches 

 fall into three groups, which are tenne(l hil)ial, nasal, and pal}tel)ral l)ranehes. 



The orbital or temporo-malar nerve passes uj)war(ls and forwards through 

 the spheno-niaxillary lissure l)y which it enters the orhit, and teiniinates hy divid- 

 ing into two l)ranches, temporal and malar. The temporal branch conimunicates 

 Avith the lachrymal nerve, and then runs forwards tln-ough the periosteum on the 

 outer wall of the orl)it, and traverses the spheno-malar foramen. It enters the 

 temjjoral fossa and pierces the deeper of- the two lamellae of the temporal fascia. 

 It runs outwards for about a quarter of an inch in the fat between the two lamella' 

 of the fascia, and pierces the superficial lamella about an inch above the superior 

 border of the zygoma; here it forms a well-marked communication with the tem- 

 ])oral l:)ranch of the facial nerve, and then ramifies in the integument of the anterior 

 temporal region. The malar branch (ramus subcutaneous malae) runs for- 

 wards in the loose fatty tissue of the orl)it, and ])asses through the malar foramen. 

 It })ierces the orl)icularis palpebrarum and su])})lies a small area of skin oA'cr the 

 prominence of the cheek. It communicates with the malar l)ranch of the facial nerve. 



The spheno-palatine nerves are two stout twigs which pass downwards to 

 Meckel's ganglion, of which they form the sensory roots; most of the nerve- 

 fibres pass on the inner side of the ganglion without traversing the ganglionic 

 substance, but it is more convenient to trace these nerves with the branches of the 

 ganglion. 



The posterior superior dental nerves, usually two in nunil>er, pass down- 

 wards and outwards through tlie pterygo-maxillary fissure. They furnish several 

 twigs to the gums ( nervuli gingivales) and adjacent part of the mucous membrane 

 of the cheek. They then enter foramina in the maxilla, follow the curve of the 

 alveolar arch through minute canals in the bone above the roots of the molar teeth, 

 and end by communicating in a plexiforrn manner with the middle dental nerve. 

 They give off minute branches to the mucous membrane of the antrum, and furnish 

 three twigs to each of the molar teeth. These twigs enter the foramina at the ti])s 

 of the fangs of the teeth and ramify in the pulp. 



The middle and anterior superior dental nerves are small l)ranches which 

 pass through canals in the substance of tin' maxilla to su])ply the incisor, canine, 

 and bicuspid teeth and the corresponding regions of the ginns. In the upper, and 

 more particularly in the lower, ])arts of these canals the nerves are surrounded on 

 all sides by thick bone; but in the middle part, where they are traversing the 

 anterior w^all of the antrum, th&y are surrounded by a mere shell of bone, which is 

 not infrequently deficient on the deep surface, so that the nerves may lie in grooves 

 in the anterit)r w^all of the antrum between the bone and mucous membrane. In 

 this situation the nerves furnish twigs to the antrum. The middle dental nerve 

 enters a foramen at the posterior part of the infraorliital canal. It sup])lies the 

 bicuspid teeth, and communicates with the anterior and posterior dental nerves. It 

 may l)e wanting. The anterior dental nerve enters a canal close to the infni- 

 orljital foramen, and su])})lies the incisor and canine teeth. It gives off a nasal 

 branch, which passes through a minute canal in the bone and enters the anterior 

 ])art of the inferior meatus. Here it ramifies in the mucous mend)rane, and com- 

 municates with the naso-palatine nerve from Meckel's ganglion. It connnunicates 

 with the middle dental nerve. 



Two stuall gangliform enlargements are ooeasionally found on the plexiforrn arch formed hy 

 the dental nerves. One of these, tlie ganglion of Valentin, is situated above the root of the 

 second l)icuspid at the junction of the middle and posterior dental nerves. The other, the 

 ganglion of Bochdalek, is placed on the junction of the anterior and middle dental nerves. 



The labial branches, usually four in number, are the largest of the tln-ee 

 terminal divisions of the maxillary nerve. They pass downwards, S])reading out as 

 they descend, under cover of the levator labii superioris muscle, and ramify in the 

 structures forming the upper lip, very large twigs being supplied to the mucous 

 membrane. 



The nasal branches, three or four in number, are intermediate in size. They 

 pass inwards under cover of the levator labii sui)erioris alteque nasi, and supply the 

 integument on the lateral aspect of the nose. 



