46 BONES OF THE HEAD. 



The ascending or nasal process projects upwards from the anterior and 

 internal part of the bone. Its surfaces are continuous with the external 

 and internal surfaces of the bone ; its internal surface, towards its summit, 

 is rough for articulation with the lateral mass of the ethmoid ; its anterior 

 border is rough for articulation with the nasal bone, and its summit serrated 

 for articulation with the frontal. Posteriorly, it articulates by a linear edge 

 with the lachrymal bone ; and external to this it presents a well-marked groove 

 for the lachrymal sac, the lachrymal groove, which is continued downwards 

 on the inner surface of the bone, between this process and the orbital plate, 

 and is converted into a canal by the lachrymal and inferior turbinated 

 bones. 



The orbital service passes forwards to the margin of the orbit, and back- 

 wards to the spheno-maxillary fissure, and is bounded externally by the surface 

 for the malar bone, and internally by the lachrymal groove and a rough edge 

 which articulates with the lachrymal, ethmoid, and palate bones. It is inter- 

 rupted by a groove which commences in its posterior border, and leads for- 

 wards into a complete canal, the infra- orbital, of which the infra-orbital 

 foramen is the anterior termination. At the inner and fore-part of the orbi- 

 tal surface is a minute depression, which gives origin to the inferior oblique 

 muscle of the eye. 



The nasal surface presents an oblique rough line beneath the ascending 

 process, for articulation with the inferior turbinated bone, and behind that 

 process the lachrymal groove. Behind the lachrymal groove is the large 

 opening into the sinus ; below and behind the sinus the surface is rough for 

 articulation with the palate bone ; and traversing the lower part of this 

 roughness is a smoother groove, passing downwards and forwards from the 

 posterior margin, and completing with the palate bone the posterior palatine 

 canal. 



The maxillary sinus, or antrum of Highmore y is a large cavity lying 

 above the molar teeth and below the orbital plate, lined in the fresh state 

 by mucous membrane, and communicating with the middle meatus of the 

 nose. Its orifice is considerably diminished by contiguous bones, viz., by 

 the uncinate process of the ethmoid, the inferior turbinated bone, and the 

 palate bone. 



THE PALATE BONE. 



The palatal or palate bone forms the back part of the palate, and the 

 lateral wall of the nose between the superior maxillary bone and the 

 internal pterygoid process. In form it has a general resemblance to the 

 letter L, consisting of a horizontal and a vertical plate and three processes, 

 viz., the pyramidal process, extending outwards and backwards from the 

 junction of the horizontal and vertical plates, and the orbital and sphenoidal 

 processes, surmounting the vertical plate. 



The palate bone articulates with its fellow, and with the superior maxillary, 

 ethmoid, sphenoid, vomer, and inferior turbinated bone. 



The horizontal or palate plate presents posteriorly a thin free bor- 

 der, forming the limit of the hard palate, and giving attachment to the 

 soft palate or velum ; anteriorly it articulates with the palate plate of the 

 superior maxillary bone, and internally by a thick serrated border with its 

 fellow of the opposite side, forming with it a ridge for articulation with the 

 vomer, continuous with that of the superior maxillaries ; externally, at its 

 junction with the vertical plate, it is grooved by the extremity of the 

 posterior palatine canal. Its superior surface is smooth, and forms the back 



