88 OSTEOLOGY. 



boundary of the spheno-maxillary fissure : occasionally, no such non-articular 

 margin exists, the fissure being completed by the direct junction of the maxillary 

 and sphenoid bones, or by the interposition of a small Wormian bone in th'e 

 angular interval between them. On the upper surface of the orbital process are 

 seen the orifices of one or two temporo-malar canals ; one of these usually opens 

 on the posterior surface, the other, occasionally two, on the facial surface : they 

 transmit filaments (temporo-malar) of the orbital branch of the superior maxillary 

 nerve. The maxillary process is a rough triangular surface, which articulates with 

 the superior maxillary bone. The zygomatic process, long, narrow, and serrated, 

 articulates with the zygomatic process of the temporal bone. Of the four borders, 

 the superior or orbital is smooth, arched, and forms a considerable part of the 

 circumference of the orbit. The inferior or zygomatic is continuous with the 

 lower border of the zygomatic arch, affording attachment by its rough edge to the 

 Masseter muscle. The anterior or maxillary border is rough, and bevelled at the 

 expense of its inner table, to articulate with the superior maxillary bone ; affording 

 attachment by its outer margin to the Levator labii superioris proprius, just at its 

 point of junction with the superior maxillary. The posterior or temporal border, 

 curved like an italic/, is continuous above with the commencement of the temporal 

 ridge ; below, with the upper border of the zygomatic arch ; it affords attachment 

 to the temporal fascia. 



Development. By a single centre of ossification, which appears at about the 

 same period when ossification of the vertebras commences. 



Articulations. "With four bones ; three of the cranium, the frontal, sphenoid, and 

 temporal ; and one of the face, the superior maxillary. 



Attachment of Muscles. Levator labii superioris proprius, Zygomaticus major 

 and Zygomaticus minor, Masseter, and Temporal. 



THE PALATE BONES. 



The Palate Bones are situated at the back part of the nasal fossae ; they are two 

 in number, one on each side, wedged in between the superior maxillary and the 

 pterygoid process of the sphenoid. Each bone assists in the formation of three 

 cavities, the floor and outer wall of the nose, the roof of the mouth, and the floor 

 of the orbit ; and enters into the formation of three fossae, the zygomatic, spheno- 

 maxillary, and pterygoid. In form, the palate bone somewhat resembles the letter 

 L, and may be divided into an inferior or horizontal plate, and a superior or 

 vertical plate. 



The Horizontal Plate is thick, of a quadrilateral form, and presents two surfaces 

 and four borders. The superior surface, concave from side to side, forms the back 

 part of the floor of the nares. The inferior surface, slightly concave and rough, 

 forms the back part of the hard palate. At its posterior part may be seen a 

 transverse ridge, more or less marked, for the attachment of the aponeurosis of the 

 Tensor palati muscle. At the outer extremity of this ridge is a deep groove, con- 

 verted into a canal by its articulation with the tuberosity of the superior maxil- 

 lary bone, and forming the posterior palatine canal. Near this groove, the orifices 

 of one or two small canals, accessory posterior palatine, may frequently be seen. 

 The anterior border is serrated, bevelled at the expense of its inferior surface, and 

 articulates with the palate process of the superior maxillary bone. The posterior 

 border is concave, free, and serves for the attachment of the soft palate. Its 

 inner extremity is sharp and pointed, and, when united with the opposite bone, 

 forms a projecting process, the posterior nasal spine, for the attachment of the 

 Azygos uvulae. The external border is united with the lower part of the perpen- 

 dicular plate almost at right angles. The internal border, the thickest, is serrated 

 for articulation with its fellow of the opposite side ; the superior edge is raised 

 into a ridge, which, united with the opposite bone, forms a crest in which the 

 vomer is received. 



