SUPERIOR MAXILLARY BONE. 161 



irregular opening leading into the antrum of Highmore. At the upper border 

 of this aperture are numerous broken cellular cavities, which, in the articulated 

 skull, are closed in by the ethmoid and lachrymal bones. Below the aperture 

 is a smooth concavity which forms part of the inferior meatus of the nose, tra- 

 versed by a fissure, the maxillary fissure, which runs from the lower part of 

 the orifice of the antrum obliquely downwards and forwards, and receives the 

 maxillary process of the palate bone. Behind it is a rough surface which arti- 

 culates with the perpendicular plate of the palate bone, traversed by a groove, 

 which, commencing near the middle of the posterior border, runs obliquely 

 downwards and forwards, and forms, when completed by its articulation with 

 the palate bone, the posterior palatine canal. In front of the opening of the 

 antrum is a deep groove, converted into a canal by the lachrymal and inferior 

 turbinated bones, which is coated with mucous membrane, and called the nasal 

 duct. More anteriorly is a well-marked rough ridge, the inferior turbinated 

 crest, for articulation with the inferior turbinated bone. The concavity above 

 this ridge forms part of the middle meatus of the nose ; whilst that below it 

 forms part of the inferior meatus. The inferior division of this surface is con- 

 cave, rough, and 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 

 outwards, 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, its anterior wall by the facial, 

 and its posterior by the zygomatic surface. 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 contracted by its articulation with the ethmoid above, 

 the inferior turbiuated below, and the palate bone behind. 1 In the articulated 

 skull, this cavity communicates with the middle meatus of the nose generally 

 by two small apertures left 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 Iamiua3 

 of bone, similar to those seen in the sinuses of the cranium; and on its poste- 

 rior 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 ; 2 in 

 some cases the floor is perforated 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 turner, 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 back- 

 wards into the zygomatic fossa, and downwards 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 zygomatic fossa ; above, it is rough and serrated for articulation with 

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



1 In some cases, at any rate, the lachrymal bone encroaches slightly on the anterior superior 

 portion of the opening, and assists in forming the inner wall of the antrum. 



* The number of teeth whose fangs are in relation with the floor of the antrum is variable. 

 The antram ''may extend so as to be in relation to all the teeth of the true maxilla, from the 

 canine to the dt-ns sapientice." See Mr. Suiter on Abscess of the Antrum, in a System of Sur- 

 gery, edited by T. HOLMES, vol. iv. p. 2o. 

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