34 OSTEOLOGY. 



uneven, and perforated by numerous small foramina for the passage of nutrient 

 vessels. 



The Antrum of Highmore, or Maxillary Sinus, is a large triangular-shaped 

 cavity, hollowed out of the body of the maxillary bone ; its apex, directed out- 

 wards, is formed by the malar process ; its base, by the outer wall of the nose. 

 Its walls are everywhere exceedingly thin, its roof being formed by the orbital 

 plate ; its floor by the alveolar process, bounded in front by the facial surface, and 

 behind by the zygomatic. Its inner wall, or base, presents, in the disarticulated 

 bone, a large irregular aperture, which communicates with the nasal fossa?. The 

 margins of this aperture are thin and ragged, and the aperture itself is much con- 

 tracted by its articulation with the ethmoid above, the inferior turbinated below, 

 and the palate bone behind. In the articulated skull, this cavity communicates 

 with the middle meatus of the nose, generally by two small apertures Jeft between 

 the above-mentioned bones. In the recent state, usually only one small opening 

 exists, near the upper part' of the cavity, sufficiently large to admit the end of a 

 probe, the other being closed by the lining membrane of the sinus. 



Crossing the cavity of the antrum are often seen several projecting Iamina3 of 

 bone, similar to those seen in the sinuses of the cranium; and on its posterior wall 

 are the posterior dental canals, transmitting the posterior dental vessels and nerves 

 to the teeth. Projecting into the floor are several conical processes, corresponding 

 to the roots of the first and second molar teeth ; in some cases, the floor is per- 

 forated by the teeth in this situation. It is from the extreme thinness of the walls 

 of this cavity, that we are enabled to explain how a tumor, growing from the 

 antrum, encroaches upon the adjacent parts, pushing up the floor of the orbit, and 

 displacing the eyeball, projecting inward into the nose, protruding forwards on to 

 the cheek, and making its way backwards into the zygomatic fossa, and down- 

 wards into the mouth. 



The Malar Process is a rough triangular eminence, situated at the angle of 

 separation of the facial from the zygomatic surface. In front, it is concave, 

 forming part of the facial surface ; behind, it is also concave, and forms part of the 

 temporal fossa ; above, it is rough and serrated for articulation with the malar 

 bone ; whilst, below, a prominent ridge marks the division between the facial and 

 zygomatic surfaces. 



The Nasal Process is a thick triangular plate of bone, which projects upwards, 

 inwards, and backwards, by the side of the nose, forming part of its lateral 

 boundary. Its external surface is concave, smooth, perforated by numerous fora- 

 mina, and gives attachment to the Levator labii superioris alasque nasi, the 

 Orbicularis palpebrarum, and Tendo oculi. Its internal surface forms part of the 

 inner wall of the nose ; it articulates above with the frontal, and presents a rough 

 uneven surface, which articulates with the ethmoid bone, closing in the anterior 

 ethmoid cells ; below this is a transverse ridge, the superior turbinated crest, for 

 articulation with the middle turbinated bone of the ethmoid, bounded below by a 

 smooth concavity, which forms part of the middle meatus ; below this is the inferior 

 turbinated crest, already described, for articulation with the inferior turbinated 

 bone ; and still more inferiorly, the concavity which forms part of the inferior 

 meatus. The anterior border of the nasal process is thin, directed obliquely 

 downwards and forwards, and presents a serrated edge for articulation with the nasal 

 bone : its posterior border is thick, and hollowed into a groove for the nasal duct. 

 Of the two margins of this groove, the inner one articulates with the lachrymal 

 bone, the outer one forms part of the circumference of the orbit. Just where 

 the latter joins the orbital surface is a small tubercle, the lachrymal tubercle; 

 this serves as a guide to the surgeon in the performance of the operation for 

 fistula lacrymalis. The lachrymal groove in the articulated skull is converted 

 into a canal by the lachrymal bone, and lachrymal process of the inferior tur- 

 binated ; it is directed downwards, and a little backwards and outwards, is about 

 the diameter of a goose-quill, slightly narrower in the middle than at either 

 extremity, and lodges the nasal duct. 



