104 DISSECTION OF THE NECK. 



orbit is now loose, and is to be removed with the temporal muscle. If the 

 part of the roof of the orbit, which is left, should interfere with the sight 

 of the contents of the cavity, let it be taken away with a bone-forceps. 



The description of the orbit (p. 51) will serve in a general way for the 

 right cavity. 



The superior maxillary division of the fifth nerve, in its course to the 

 face, occupies successively the skull, the spheno-maxillary fossa, and the 

 infra-orbital canal. 



The beginning of the nerve in the cranium has been already demon- 

 strated (p. 31). 



Dissection. In the spheno-maxillary fossa the nerve can be partly seen 

 by the dissection already made for the orbit, and its exposure here will be 

 completed by removing the fat, and cutting away some of the wing of the 

 sphenoid bone, so as to leave only an osseous ring round the nerve at its 

 exit from the skull. In the fossa the student seeks the following offsets, 

 the orbital branch entering the cavity of the orbit ; branches to Meckel's 

 ganglion which descend in the fossa ; and a dental branch along the back 

 of the upper jaw. 



To follow onwards the nerve in the floor of the orbit, the contents of 

 the cavity having been taken away, the bony canal in which it lies must 

 be opened to the face. Near the front of the orbit the anterior dental 

 branch is to be traced downwards for some distance in the bone. The 

 infraorbital vessels are prepared with the nerve. 



The SUPERIOR MAXILLARY NERVE (fig. 24) commences in the Gasse- 

 rian ganglion (p. 31), and leaves the cranium by the foramen rotundum. 

 The course of the nerve is almost straight to the face, across the spheno- 

 maxillary fossa, and along the orbital plate of the superior maxilla and the 

 infraorbital canal. Issuing from the canal by the infraorbital foramen, it 

 is concealed by the elevator of the upper lip, and ends in branches to the 

 eyelid, nose, and upper lip : 



a. The orbital branch (*) arises in the spheno-maxillary fossa, and en- 

 tering the orbit, divides into malar and temporal branches (p. 60). 



b. The spheno-palatine branches ( 3 ) descend from the nerve in the 

 fossa, and supply the nose and the palate; they are connected with Meek- 

 el's ganglion, and will be dissected with it (SECTION 14). 



c. A posterior dental branch ( s ) leaves the nerve near the upper jaw. 

 It enters a canal in the maxilla, and supplies branches to the molar teeth 

 and the lining membrane of the antrum ; it joins the anterior dental branch 

 near the teeth. Before entering the canal it furnishes one or more offsets 

 to the gums and the buccinator muscle. 



d. The anterior dental branch ( 6 ) quits the nerve trunk in the floor of 

 the orbit, and descends to the anterior teeth in a special canal in front of 

 the antrum: it is distributed by two branches. One (inner) gives nerves 

 to the incisor and canine teeth, and furnishes one or two filaments to the 

 lower meatus of the nose; the other (outer) ends by supplying the bicuspid 

 teeth. 



e. Before the trunk ends in the facial branches, it supplies a small pal- 

 pebral offset to the lower eyelid ; this is directed upwards to the lid in a 

 groove in the margin of the orbit. 



f. Infraorbital or facial branches ( 7 ). These are larger than the other 

 offsets of the nerve, and form its terminal ramifications. Some incline 

 inwards to the side of the nose, and the rest descend to the upper lip. 

 Near the orbit they are crossed by branches of the facial nerve (fig. 9, u ), 



