THE PALATE BONES. 93 



of the pterygoid fossa, affording attachment to the Internal pterygoid muscle ; 

 whilst the lateral surfaces are rough and uneven, for articulation with the anterior 

 border of each pterygoid plate. A few fibres of the Superior constrictor arise from 

 the tuberosity of the palate bone. The base of this process, continuous with the 

 horizontal portion of the bone, presents the apertures of the accessory descending 

 palatine canals, through which pass the two smaller descending branches of 

 Meckel's ganglion ; whilst its outer surface is rough for articulation with the inner 

 surface of the body of the superior maxillary bone. 



The superior border of the vertical plate presents two well-marked processes 

 separated by an intervening notch or foramen. The anterior, or larger, is called 

 the orbital process ; the posterior, the sphenoidal. 



The Orbital Process, directed upward and outward, is placed on a higher level 

 than the sphenoidal. It presents five surfaces, which enclose a hollow cellular 

 cavity, and is connected to the perpendicular plate by a narrow, constricted neck. 

 Of these five surfaces, three are articular, two non-articular or free surfaces. The 

 three articular are the anterior or maxillary surface, which is directed forward, 

 outward, and downward, is of an oblong form, and rough for articulation with 

 the superior maxillary bone. The posterior or sphenoidal surface is directed 

 backward, upward, and inward. It ordinarily presents a small, open cell, which 

 communicates with the sphenoidal cells, and the margins of which are serrated 

 for articulation with the vertical part of the sphenoidal turbinated bone. The 

 internal or ethmoidal surface is directed inward, upward, and forward, and 

 articulates with the lateral mass of the ethmoid bone. In some cases the cellular 

 cavity above mentioned opens on this surface of the bone ; it then communicates 

 with the posterior ethmoidal cells. More rarely it opens on both surfaces, and 

 then communicates both with the posterior ethmoidal and the sphenoidal cells. 

 The non-articular or free surfaces are the superior or orbital, directed upward and 

 outward, of triangular form, concave, smooth, and forming the back part of the 

 floor of the orbit ; and the external or zygomatic surface, directed outward, 

 backward, and downward, of an oblong form, smooth, lying in the spheno-maxil- 

 lary fossa, and looking into the zygomatic fossa. The latter surface is separated 

 from the orbital by a smooth, rounded border, which enters into the formation 

 of the spheno-maxillary fissure. 



The Sphenoidal Process of the palate bone is a thin, compressed plate, much 

 smaller than the orbital, and directed upward and inward. It presents three 

 surfaces and two borders. The superior surface, the smallest of the three, 

 articulates with the under surface of the sphenoidal turbinated bqne ; it presents a 

 groove, which contributes to the formation of the pterygo-palatine canal. The 

 internal surface is concave, and forms part of the outer wall of the nasal fossa. 

 The external surface is divided into an articular and a non-articular portion : the 

 former is rough, for articulation with the inner surface of the internal pterygoid 

 plate of the sphenoid ; the latter is smooth, and forms part of the spheno-maxil- 

 lary fossa. The anterior border forms the posterior boundary of the spheno- 

 palatine foramen. The posterior border, serrated at the expense of the outer 

 table, articulates with the inner surface of the internal pterygoid plate. 



The orbital and sphenoidal processes are separated from one another by a deep 

 notch, which is converted into a foramen, the spheno-palatine, by articulation 

 with the sphenoidal turbinated bone. Sometimes the two processes are united 

 above, and form between them a complete foramen, or the notch is crossed by one 

 or more spiculae of bone, so as to form two or more foramina. In the articulated 

 skull this foramen opens into the back part of the outer wall of the superior 

 meatus, and transmits the spheno-palatine vessels and the superior nasal and 

 naso-palatine nerves. 



Development. From a single centre, which makes its appearance about the 

 second month at the angle of junction of the two plates of the bone. From this 

 point ossification spreads inward to the horizontal plate, downward into the 

 tuberosity, and upward into the vertical plate. In the foetus the horizontal plate 



