THE NASAL AND MALAR BONE. 



209 



FRONTAL 



Crest 



Groove for 

 nasal nerve 



Right nasal bone, outer and inner aspects. 



THE NASAL BONE. 



The two nasal bones ^ bound the anterior nasal opening above. Each one is a 

 four-sided plate with an outer and an inner surface. The upper end is thick and 

 jagged, articulating with the frontal above and also behind. The anterior border, 

 which articulates with its fellow, is thick above and thin below. When the two 

 bones are in place, the united upper portions of these borders form posteriorly the 

 7iasal crest, which articulates 



with the nasal spine of the Pig. 238. 



frontal, and sometimes with 

 the vertical plate of the eth- 

 moid below it. The pos- 

 terior border joins the as- 

 cending process of the 

 maxilla. The thin lower 

 border, slanting downward 

 and outward, has one or 

 two indentations. The outer 

 surface is broader below 

 than above. It is depressed 

 in the upper third, and has 

 there a foramen for a vein. 

 The extreme upper part of 

 the inner surface is rough 

 to join the frontal. Below 

 this it is smooth where it 

 forms the front of the nasal 

 chamber ; the lower part of the inner surface sometimes seems hollowed out. A 

 vertical groove for the nasal nerve ends near the notch in the lower border. 



Articulations. — The nasal bone articulates with the frontal, ethmoid, superior 

 maxilla, and the opposite nasal. 



Development. — Ossification spreads from a centre appearing about the eighth 

 week of fcetal life. At first the bone is broad and short. Occasionally a little 

 Wormian bone is found in the median line between the nasals and the frontal. The 

 two bones sometimes coossify, after the fashion of apes. Either a vertical or a trans- 

 verse suture may be found. 



THE MALAR BONE. 



This bone^ forms the prominence of the cheek, the outer border of the orbit, 

 most of the wall separating the orbit from the temporal fossa, and completes the 

 zygomatic arch. For simplicity of description it is best to consider it a diamond- 

 shaped bone, with an outer and an inner surface, four angles, four borders, and one 

 important process, the orbital, which is neither an angle nor a border. The outer 

 surface presents a slight prominence, the tuberosity,^ a little below the middle. The 

 surface is nearly smooth, except that near the lower border there is often a certain 

 roughness extending onto the zygomatic process for the origin of the masseter muscle. 

 The greater part of the in?ier surface is smooth, looking towards the temporal and 

 zygomatic fossae ; but a rough space under the front angle joins the malar process of 

 the maxilla. It sometimes helps to close the antrum, in which case a part of it is 

 smooth, being lined with mucous membrane. The superior angle, or f-ontal process,^ 

 joins by a rough surface the external angular process of the frontal. The posterior 

 angle, or zygomatic process ^^ more prominent below than above, joins the zygomatic 

 process of the temporal, passing below it. The anterior and the inferior angks 

 have no special names. The postero-superior, or temporal border, is at first vertical, 

 becoming horizontal towards the hind end. Near the beginning there is a posterior 

 projection, the marginal process, which varies considerably. The postero-inferior, 

 or masseteric border, slightly irregular, is free, forming the lower edge of the front of 

 the zygoma. The antero-inferior, or maxillary border, is slightly concave. It articu- 



^ Ossa nasalia. - Os zygomaticum. " Tuberositas malaris. * Processus frontosphenoidalis. •' Processus temporalis. 



