PALATE BONES. 49 



cheek. It is divisible into an external and internal surface, and 

 four processes, the frontal, orbital, maxillary, and zygomatic. The 

 external surface is smooth and convex, and pierced by .several 

 small openings which give passage to filaments of the temporo- 

 malar nerve and minute arteries. The internal surface is concave, 

 partly smooth and partly rough; smooth where it forms part of 

 the temporal fossa, and rough where it articulates with the superior 

 maxillary bone. 



The frontal process ascends perpendicularly to form the outer 

 border of the orbit, and articulate with the external angular process 

 of the frontal bone. The orbital process is a thick plate, which pro- 

 jects inwards from the frontal process, and unites with the great 

 ala of the sphenoid to constitute the outer wall of the orbit. It is 

 pierced by several small foramina for the passage of temporo-malar 

 filaments of the superior maxillary nerve. The maxillary process 

 is broad, and articulates with the superior maxillary bone. The 

 zygomatic process, narrower than the rest, projects backwards to 

 unite with the zygoma of the temporal bone. 



Developement. By a single centre. 



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

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

 bone. 



Attachment of Muscles. To six ; orbicularis palpebrarum, levator 

 labii superioris proprius, zygomaticus minor and major, masseter, 

 and temporal. 



PALATE BONES. The palate bones are situated at the posterior 

 part of the nares, where they enter into the formation of the palate, 

 the side of the nose, and the posterior part of the floor of the orbit ; 

 hence they might with great propriety be named the palato-naso- 

 orbital bones. Each bone resembles in general form the letter L, 

 and is divisible into a horizontal plate, a perpendicular plate, and a 

 pterygoid process or tuberosity. 



The horizontal plate is quadrilateral ; and 

 presents two surfaces, one superior, which Fig. 20.* 



enters into the formation of the floor of the 

 nares, the other inferior, forming the posterior 

 part of the hard palate. The superior surface 

 is concave and rises towards the middle line, 

 where it unites with its fellow of the opposite 

 side and forms a crest, which articulates with 

 the vomer. The inferior surface is marked by 

 a slight transverse ridge, to which is attached 

 the tendinous expansion of the tensor palati 

 muscle, and near to the external border are two 

 openings, the posterior palatine foramina, which 

 transmit th6 posterior palatine nerves and artery. The posterior 



* A posterior view of the palate bone in its natural position ; it is slightly turned to 

 one side to obtain a sight of the internal surface of the perpendicular plate (2.) 1. The 

 horizontal plate of the bone ; its upper or nasal surface. 2. The perpendicular plate ; 



7 



