174 OSTEOLOGY. 



the sphenoid in front and the occipital bone behind. Stretching forwards from the 

 squamous part of the temporal in front is seen the zygomatic process which, by its 

 union with the zygomatic bone, completes the formation of the zygomatic arch. 



Palatum Durum. Studying next the various parts in detail, the hard palate 

 may be first examined. Of horse-shoe shape as a rule, it presents many varieties of 

 outline and size. Formed by the palatine processes of the maxillae in front 

 and the horizontal parts of the palate bones behind, its circumference in front 

 and at the sides corresponds to the superior alveolar arch, in which are embedded 

 the sixteen teeth of the two maxillse ; posteriorly the edge of the hard palate is 

 thin, presenting in the median plane a pointed process, the posterior nasal spine, 

 on either side of which the posterior free border is sharp and lunated. The vault 

 of the palate, which is concave from side to side, and from before backwards, varies 

 in depth according to the projection and development of the alveolar processes. 

 When the teeth are shed and the alveoli are absorbed, the palate becomes shallow 

 and flat. Kunning throughout its entire length in the median plane is the 

 median palatine suture, which separates the palatine processes of the maxillse 

 in front and the horizontal parts of the palate bones behind. A little behind 

 the central incisor teeth, and in the line of this suture, is a little pit, the 

 foramen incisivum. At the bottom of this may be seen the openings of some 

 small canals, varying in number from one to four; these are usually described 

 as arranged in two pairs, the one pair placed side by side, the other lying in the 

 median plane in front and behind. The former are called the foramina of Stenson, 

 and transmit the terminal twigs of the greater palatine arteries which ascend to 

 reach the nasal cavities. The latter, called the foramina of Scarpa, open, the 

 anterior into the left, the posterior into the right nasal cavity, and afford passage for 

 the fine filaments of the left and right naso-palatine nerves, respectively. About 

 half an inch (12 mm.) in front of the posterior nasal spine the median palatine 

 suture is crossed at right angles by the transverse palatine suture. This, which 

 indicates the line of union of the palatine processes of the maxillse with the 

 horizontal parts of the palate bones, passes transversely laterally on either side until 

 it reaches the medial aspect of the base of the alveolar process, along which it 

 turns backwards, to disappear within the foramen palatinum majus (greater palatine 

 foramen), the aperture of which lies just medial to the root of the dens serotinus 

 (wisdom molar). Through this there pass the greater palatine artery and the 

 large anterior palatine nerve. Leading from this foramen is a groove which 

 curves forwards immediately to the medial side of the alveolar arch ; not infrequently 

 the medial edge of this groove forms a thin and sharp ridge on the surface of the 

 palate. In this groove are lodged the afore-mentioned vessels and nerves. The 

 surface of the palate in front of the transverse suture is rough, pitted for the palatine 

 glands, and pierced by numerous small vascular foramina ; the part of the palate 

 behind the suture, formed by the under surface of the horizontal part of the palate 

 bone, is much smoother. From this there rises, just posterior to the greater 

 palatine foramen, a thin sharp crest, which curves medially immediately in 

 front of the posterior free edge ; to this are attached some of the tendinous fibres 

 of the tensor veli palatini muscle. 



Pterygoid Processes. Buttressed against the posterior extremities of the 

 alveolar arch are the pterygoid processes of the sphenoid. If carefully examined, 

 these will be seen not to lie in actual contact with the maxillae, but to be separated 

 from them by the triangular wedge-shaped pyramidal processes of the palate 

 bones. It is these latter which are pierced by the foramina palatina minora (lesser 

 palatine canals), which lie just behind the greater palatine foramen, and through 

 which pass the lesser palatine nerves. As here displayed, the pterygoid processes of 

 the sphenoid lie on either side of the opening of the choanse (O.T. posterior nares) ; 

 each consists of two laminae, a medial and a lateral ; the latter is the broader, 

 and is directed backwards and slightly laterally. Its lateral surface has been 

 already studied in connexion with the infra- temporal fossa (p. 168). Medially it is 

 separated from the medial pterygoid lamina by the pterygoid fossa, wherein is lodged a 

 considerable part of the internal pterygoid muscle. The floor of the fossa is formed 

 in greater part by the coalescence of the two pterygoid laminae ; but at the level of 



