114 A MANUAL OF ANATOMY 



has an inclination downwards as well as inwards. It forms part 

 of the outer wall and roof of the nasal fossa. The external or 

 spheno-maxillary surface forms part of the inner wall of the spheno- 

 maxillary fossa. The anterior border bounds the spheno-palatine 

 notch posteriorly, and may be projected over it to join the orbital 

 process. The posterior border articulates with the internal ptery- 

 goid plate of the sphenoid. The internal border articulates with 

 the ala of the vomer. 



The spheno-palatine notch is situated between the orbital and 

 sphenoidal processes, and is converted into a foramen usually by 

 the inferior surface of the body of the sphenoid, representing the 

 part formed by a sphenoidal spongy bone. It leads from the 

 spheno-maxillary fossa into the superior meatus of the nose, and 

 transmits the internal branches of the spheno-palatine or Meckel's 

 ganglion, and spheno-palatine artery. 



The bone derives its blood-supply from the spheno-palatine, 

 descending palatine, and pterygo-palatine branches of the internal 

 maxillary artery. 



Articulations. — The palate bone articulates with six bones, as 

 follows: the superior maxilla, inferior turbinate, ethmoid, vomer, 

 sphenoid, and its fellow. 



Structure. — The bone is very thin, especially over the upper 

 part of the perpendicular plate. 



Varieties. — (i) The groove for the posterior palatine canal may be bridged 

 over. (2) The external accessory palatine canal may be absent. (3) The 

 spheno-palatine notch may be converted into a foramen by a forward 

 extension of the sphenoidal process. 



Ossiflcation. — The palate bone is ossified in membrane from one primary 

 centre. The primary centre appears about the seventh week, at the angle of 

 junction between the horizontal and vertical plates, or in the vertical plate 

 (Fawcett). There may be a secondary centre for the orbital process. 



The Vomer. 



The vomer is situated in the median plane, and forms part of 

 the septum of the nose. It presents two surfaces, four borders, 

 and an anterior extremity. The surfaces are disposed laterally, 

 and each looks into the corresponding nasal fossa. Traversing 

 each there is a groove, directed forwards and downwards, for the 

 naso-palatine nerve. 



The superior border is characterized by two thick, everted alae, 

 separated by a groove, which receives the rostrum of the sphenoid, 

 Each ala by its upper aspect fits against the inferior surface of 

 the body of the sphenoid, and the lateral margin of each meets 

 the vaginal process of that bone, and also articulates with the 

 internal border of the sphenoidal process of the palate bone. The 

 inferior border is irregular, and is received into the groove which 

 marks the nasal crests of the palatal plates of the superior maxillae 

 and palate bones. The anterior border is sloped downwards and 



