THE SUPERIOR MAXILLA. 201 



becomes a canal, opening at the corresponding foramen in front. Occasionally a 

 suture marks the course of the canal. The internal wall of the body presents 

 on the separate bone a very large opening into the antrum, or maxillary sinus, 

 which is much reduced when the other bones are in place. In front of this opening 

 the wall is smooth and concave, forming a part of the lachrymal groove. Near the 

 level of the top of the body there is the rough horizontal inferior turbinate crest for 

 articulation with that bone. The wall at the back of this surface has a vertical 

 groove, which, when the palate bone is in place, forms part of the posterior pa /ati?ie 

 canal, opening near the back of the hard palate and transmitting the descending 

 palatine artery and the anterior palatine nerve. 



The malar and the alveolar processes have been incidentally described. The 

 nasal or ascending process rises at the inner side of the orbit. It is thin below, with 

 an outer surface towards the face and an inner towards the nose. The top is thick 

 and rough, joining the frontal. The lachrymal groove^ for the tear-sac and the nasal 

 duct begins on its outer surface and passes down behind it, making a deep notch at 

 the front of the orbital plate. The lower part of the process extends down as far as 

 the inferior turbinate crest, forming, with the lachrymal, the inner side of the groove. 

 The point of junction of the front border of the groove with the orbital plate is 

 usually marked by the lachrymal tubercle. The inner side shows above at the pos- 

 terior border some cellular spaces completing the anterior ethmoidal cells, bounded 

 below by a ridge, the crista ethmoidalis, which articulates with the front of the middle 

 turbinate bone. Below it the bone is concave, forming part of the vestibule of the 

 nose ; above it is plane and marked with vascular grooves. 



The palatal process projects inward from the anterior two-thirds of the body 

 and joins the alveolar process in front. It is very smooth above, the mucous mem- 

 brane being lightly attached to it. It is slightly concave from side to side, and has 

 a raised edge in front. It is also raised along the median line to form the nasal crest^ 

 with its fellow. The front of this ridge, called the incisor crest, suddenly rises to a 

 higher level and juts out below the nose as the anterior nasal spitie. The vomer 

 rests on the ridge, except at the front, where its place is taken by the triangular 

 cartilage. The under surface of the palatal process, horizontal behind, slants down- 

 ward in front to the incisor teeth. It is rough for the firm support of the mucous 

 membrane. The median surface of the palate is rough to join with its fellow. A 

 little behind the incisors it shows a groove in the lower part, which becomes a canal 

 in the upper, and opens, into the floor of the nasal fossa of either side. Thus there 

 are two canals above and one below, like a Y placed transversely. These are the 

 canals of Ste7iso?t, which transmit an artery connecting the vessels of the nose and 

 mouth. Their common orifice is called the anterior palatine canal.'^ Into this open 

 two minute canals, the left anterior to the right, made by the junction of the bones. 

 These are the canals of Scarpa, and transmit the naso-palatine nerves. They are 

 by no means always to be found. The canals of Stenson represent the anterior 

 palatine canal of lower animals, which in them is generally double throughout. In 

 man the whole opening is usually closed by mucous membrane. The back of the 

 palate process joins the horizontal plate of the palate bone, which completes the 

 palate behind. 



The antrum or maxillary sinus* is a large cavity within the body, the shape 

 of which it follows in the main, although with many variations of size. The large 

 opening on its inner wall is much diminished when the palate, the ethmoid, and the 

 inferior turbinate are in place. It lies near the anterior end of the lateral wall of the 

 middle nasal meatus, covered by the middle turbinate. A small part of the roof of 

 the antrum is often formed by the palate bone, and sometimes the cavity extends into 

 the malar. The inner and most of the posterior and outer walls are generally very 

 thin, as is also the roof, except around the infra-orbital canal, which projects into the 

 antrum. The development outward towards the malar bone varies much, as does 

 the downward and forward growth towards the alveolar process. The lower border 

 of the antrum is usually a trifle below the level of the floor of the nares. According 

 to C. Reschreiter,^ this is a male characteristic. Be that as it may, it certainly is in 

 ^Zur INIorphologie des Sinus Maxillaris, Stuttgart, 1878. 



^ Sulcus lacrimalis. " Crista nasalis. '^ Foramen incisivum. ^ Sinus maxillaris. 



