192 THE SKELETON. 



concavity which forms part of the inferior meatus of the nasal fossae, and behind 

 it is a rough surface which articulates with the perpendicular plate of the palate 

 bone, traversed by a groove which, commencing near the middle of the posterior 

 border, runs obliquely downward and forward, 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. It is called the lachrymal groove, and lodges 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 portion of this surface below the palate process 

 is concave, rough and uneven, and perforated by numerous small foramina for the 

 passage of nutrient vessels. It enters into the formation of the roof of the mouth. 



The Antrum of Highmore, or Maxillary Sinus, is a large, pyramidal cavity 

 hollowed out of the body of the maxillary bone : its apex, directed outward, is 

 formed by the malar process ; its base, by the outer wall of the nose. Its walls 

 are everywhere exceedingly thin, and correspond to the orbital, facial, and zygo- 

 matic surfaces of the body of the bone. 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 

 turbinated below, and the palate bone behind, 1 In the articulated skull this cavity 

 communicates with the middle meatus of the nasal fossae, 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 laminae 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 ; 2 in some cases the floor is perfo- 

 rated 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 forward on 

 to the cheek, and making its way backward into the zygomatic fossa and downward 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, form- 

 ing 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 the facial and 

 zygomatic surfaces. A small part of the Masseter muscle arises from this process. 



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

 inward, and backward by the side of the nose, forming part of its lateral boundary. 

 Its external surface is concave, smooth, perforated by numerous foramina, and 

 gives attachment to the Levator labii superioris alaeque nasi, the Orbicularis 

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

 of the nose : at its upper part it presents a rough, uneven surface, which 

 articulates with the ethmoid bone, closing in the anterior ethmoidal cells ; below 

 this is a transverse ridge, the superior turbinated crest, for articulation with the 



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

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



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

 antrum " may extend so as to be in relation to all the teeth of the true maxilla, from the canine to 

 the dens sapienticE." (See Mr. Salter on Abscess of the Antrum, in a System of Surgery, edited by T. 

 Holmes, 2d ed. vol. iv. p. 356.) 



