THE HEAD. 47 



towards each other at their inferior extremity, which is flattened from 

 before to behind, these bones, though irregular in shape, offer for study 

 two faces, two borders, and two extremities. 



Faces. The external face of the palate bone is divided into three frac- 

 tions, a superior, or orbital, an inferior, or palatine, and a middle, or articular. 

 The first is smooth and slightly excavated, and participates in the forma- 

 tion of the maxillary hiatus ; it shows a small fissure, the staphyloid, which 

 reaches the palatine fraction in passing between the posterior border of the 

 bone and the alveolar tuberosity. The second is not extensive, and looks 

 backwards in consequence of the antero-posterior flattening which the bone 

 presents at its inferior extremity ; it forms part of the roof of the palate. 

 The third presents a lamellar and denticulated surface which corresponds to 

 a similar face on the supermaxillary bone, and is channeled from above to 

 below by the internal fissure of the palatine canal. 



The internal face, smooth and concave, forms part of the external wall 

 and the floor of the nasal fossa. 



Borders. The anterior is indented, near its superior 'third, by a deep 

 notch, which is often converted into a foramen, the nasal. Below this notch 

 the bone is thin and denticulated for union with the supermaxillary bone ; 

 above, its two plates separate widely from one another, giving rise to a 

 very spacious cavity which forms part of the sphenoid sinus. The posterior 

 border presents, above, a rugged crest called the palatine, flattened from side 

 to side, bent outwards, and bordered at its base and inwards by a very 

 narrow synarthrodial surface which responds to the pterygoid bone. It is 

 smooth and concave in its inferior half, and forms, with that of the opposite 

 side, a parabolic arch which circumscribes, below and at the side, the double 

 guttural orifice of the nasal cavities. 



Extremities. The superior, flattened on both sides, is bevelled on the 

 external side to articulate with the subsphenoidal process. The inferior, 

 flattened from before to behind, is curved inwards and united by simple 

 suture with that of the opposite bone. 



Structure and development. This is a very compact bone, developed from 

 a single centre of ossification. 



4. Pterygoid Bone. 1 



A small and very narrow bone, elongated from above to below, flattened 

 on both sides, and situated on the inner aspect of the subsphenoidal process, 

 but external to the vomer. 



Its external face is in contact with the palate and sphenoid bones ; 

 the internal is smooth and covered by the pharyngeal mucous membrane. 

 Its superior extremity is tapering, and concurs in forming the vidian canal ; 

 the inferior is thickened into a small pointed process (the hamular process), 

 whose apex, directed backwards, offers outwardly a groove which serves as a 

 pulley to the tendon of the tensor palati. This bone is composed entirely 

 of compact tissue, and is developed from a single centre of ossification. 



5. Zygomatic Bone. 



This bone, also designated the malar and jugal bone, is elongated from 

 above to below, flattened on both sides, and irregularly triangular in shape; 

 it is situated on the side of the face, and articulates with the supermaxillary, 



1 This bone is the representative of the internal wing of the pterygoid process in Man. 



