The temporo-zygomatic surface is smooth and concave below ; and internally there is a rough surface which rests on the malar process of the upper maxillary : about the centre or to wards the upper part of this surface is observed the internal orifice of a molar canal or a molar hole. The temporal muscle is attached to this surface.
The orbiter surface is smooth, concave, and is formed upon a plate of bone (the orbiter process), which stands inwards, and contributes to the outer wall and floor of the orbit : its op posite surface above makes part of the tempo ral fossa. On the orbitar surface we observe the orifice of a malar canal. The orbitar pro cess has an irregular summit, which receives time frontal bone ; below, it is articulated with the outer border of the orbitar plate of the sphenoid ; in the middle it corresponds to the extremity of the spheno-maxillary fissure ; and inferiorly it is united to the outer border of the orbitar plate of the upper maxillary bone.
Of the four borders two are anterior and two posterior. The anterior superior, or the orbi tar, is smooth, concave, and forms the outer and lower third of the base of the orbit. The anterior inferior, or the maxillary, rests upon the malar process of the upper maxilla from its extremity to the inferior orbitar foramen. The posterior superior, or temporal border, is waved like the letter S, and gives attachment to the temporal fascia. The posterior inferior, or masseterie border, is thick, and gives attach ment to a muscle of the same name. The four angles are, 1. thick, rough, superior or frontal, which receives the external angular process of the frontal bone; 2. the interior or orbitar, which is pointed ; and, 3. the inferior or molar, which is round, and forms the extremities of the maxillary border, and which rests on the malar process of that bone. The posterior or zygomatic is cut obliquely from above down wards and backwards, and supports the zygo matic process of the temporal bone.
Conncxions.—The malar is connected with and locked between four bones, viz, the frontal, the sphenoid, the upper maxillary, and the temporal. It contributes to form the orbit, the temporal, and the zygomatic fosse, It gives attachment to four muscles, viz. the temporal, the masseter, and the two zygomatic ; and it gives passage to malar vessels and nerves.
The structure is compact, except near its upper and lower angles, where there is some cancellous tissue.
Developemcut.—Its ossification commences in one piece about the fiftieth day, and is com pleted at birth, when the bone appears thicker, and its orbitar plate larger in proportion than in the adult : its vertical diameter is, however, narrow, and the malar holes are large.
The nasal bones (ossa nasi ; Germ. die Nascnbeine) form the upper part of the nose, and are placed between the nasal pro cesses of the upper maxillary and below the frontal bones, inclining from above downwards and forwards. They have two surfaces, and their form is quadrilateral, the vertical exceed ing the transverse diameter. They are stout and narrow above, and thin and broader below.
The anterior or cutaneous surface is smooth, covered by the integuments and pyramidalis muscle, concave from above downwards, con vex transversely. An oblique hole for the passage of vessels is usually found above the centre of one or both nasal bones, and some smaller foramina are scattered over the surface.
The posterior or pituitary surface is concave, narrow, especially above, and lined by the olfactory membrane, presenting grooves for vessels and the internal orifice of the canal (or hole) mentioned above.
The borders are four : a superior, short, thick, dentated, inclined from above down wards and backwards, and resting on the nasal notch of the frontal bone between its two in ternal angular processes : the it erior border, longer than the preceding, thin, jagged, in clining from the median line downwards and outwards, and generally presenting about its centre a slight notch for the passage for a fila ment of the nasal nerve. This border forms the upper and front part of the anterior opening of the nasal foss, and gives attachment to the lateral cartilages of the nose. The external border is the longest, and is cut obliquely for its articulation with the nasal process of the upper maxillary bone. The internal border is shorter, thick and rough above, and thin be low : it forms, on the inner aspect of the bone, in conjunction with the corresponding part of the bone of the opposite side, a ridge and groove for the reception of the nasal process or spine of the frontal bone, and for the upper and anterior border of the perpendicular plate of the etlimoid.