730 THE NERVOUS SYSTEM. 



firmer in texture. It then crosses the spheno-m axillary fossa, enters the orbit 

 through the spheno-maxillary fissure, traverses the infra-orbital canal in the floor 

 of the orbit, and appears upon the face at the infra-orbital foramen. 1 At its 

 termination the nerve lies beneath the Levator labii superioris muscle, and divides 

 into a leash of branches, which spread out upon the side of the nose, the lower 

 eyelid, and upper lip, joining with filaments of the facial nerve. 



Branches of Distribution. The branches of this nerve may be divided into four 

 groups : 1. Those given off in the cranium. 2. Those given off in the spheno- 

 maxillary fossa. 3. Those in the infra-orbital canal. 4. Those on the face. 



In the cranium . . . Meningeal. 



{Orbital or temporo-malar. 

 Spheno-palatine. 

 Posterior superior dental. 



Infra-orbital canal . / Middle superior dental. 



[ Anterior superior dental. 



( Palpebral. 

 On the face . . < Nasal. 



( Labial. 



The meningeal branch is given off directly after its origin from the Gasserian 

 ganglion ; it accompanies the middle meningeal artery and supplies the dura 

 mater. 



The orbital or temporo-malar branch arises in the spheno-maxillary fossa, 

 enters the orbit by the spheno-maxillary fissure, and divides at the back of that 

 cavity into two branches, temporal and malar. 



The temporal branch runs in a groove along the outer wall of the orbit (in the 

 malar bone), receives a branch of communication from the lachrymal, and, 

 passing through a foramen in the malar bone, enters the temporal fossa. It 

 ascends between the bone and substance of the Temporal muscle, pierces this 

 muscle and the temporal fascia about an inch above the zygoma, and is distributed 

 to the integument covering the temple and side of the forehead, communicating 

 with the facial and auriculo-temporal branch of the inferior maxillary nerve. As 

 it pierces the temporal fascia it gives off a slender twig, which runs between the 

 two layers of the fascia to the outer angle of the orbit. 



The malar branch passes along the external inferior angle of the orbit, emerges 

 upon the face through a foramen in the malar bone, and, perforating the Orbicu- 

 laris palpebrarum muscle, supplies the skin on the prominence of the cheek, and 

 is named subcutaneus malce. It joins with the facial and the palpebral branches 

 of the superior maxillary. 



The spheno-palatine branches, two in number, descend to the spheno-palatine 

 ganglion. 



The posterior superior dental branches arise from the trunk of the nerve just 

 as it is about to enter the infra-orbital canal ; they are generally two in number, 

 but sometimes arise by a single trunk, and immediately divide and pass downward 

 on the tuberosity of the superior maxillary bone. They give off several twigs to 

 the gums and neighboring parts of the mucous membrane of the cheek (superior 

 gingival branches). They then enter the posterior dental canals on the zygomatic 

 surface of the superior maxillary bone, and, passing from behind forward in the 

 substance of the bone, communicate with the middle dental nerve, and give off 

 branches to the lining membrane of the antrum and three twigs to each of the 

 molar teeth. These twigs enter the foramina at the apices of the fangs and 

 supply the pulp. 



The middle superior dental branch is given off from the superior maxillary nerve 

 in the back part of the infra-orbital canal, and runs downward and forward in a 

 special canal in the outer wall of the antrum to supply the two bicuspid teeth. It 

 communicates with the posterior and anterior dental branches. At its point of 



1 After it enters the infra-orbital canal, the nerve is frequently called the infra-orbital. 



