Skull and Hyoid 



233 



PALATE BONE. 



Each palate bone consists of : (i) a vertical plate, which is applied to the posterior 

 part of the inner surface of the body of the maxilla ; (2) a horizontal plate, which projects 

 nwards from the lower end of the vertical plate, lies in the plane of the palatine process 

 of the maxilla, and articulates mesially with its fellow of the opposite side ; (3) a 

 luberosity that projects downwards, outwards and backwards from the vertical plate, 

 and so lies behind the lower part of the back of the maxilla and separates it from the 

 pterygoid plates of the sphenoid, against which it is placed. 



The vertical plate is not only applied to the inner side of the maxilla, but extends 

 back behind the level of this bone to articulate with the front border of the internal 

 pterygoid plate, and in this way its hinder part forms the inner wall of the spheno- 

 maxillary fossa. These two articulations cause a difference in the direction of the back 



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tueen ptfryqoiZ plaits. 



FIG. 187. Right palate bone. i. Posterior aspect. Observe the deep groove for internal 

 pterygoid plate against which the bone is placed. 2. From the nasal or inner side. 3. From 

 the outer side. The greater part. A., of this surface rests against the maxilla, but a small 

 part, B., projects back beyond that bone and forms the inner wall of the spheno-maxillary 

 fossa ; the post. pal. canal runs down from this surface, between A. and the tuberosity. 



and front portions of the vertical plate : the front part (Fig. 185), being applied to the 

 maxilla, turns outward at its upper end with the maxillary surface, and thus lies between 

 the maxilla and the ethmoid and reaches the orbit, where it forms part of the floor ; 

 whereas the posterior part, following the margin of the internal pterygoid plate, turns 

 in at the top (Fig. 183) and comes to lie below the body of the sphenoid. The vertical 

 plate can be described, therefore, as terminating above in an anterior orbital process, 

 directed upwards and outwards, and a posterior sphenoidal process, directed upwards 

 and inwards. Between these two is a deep spheno-palatine notch, converted into a 

 foramen by the sphenoidal turbinate that lies above it. Sometimes a large orbital 

 process may convert the notch into a complete foramen : this has also been seen 

 double. 



The orbital process, very variable in size, has : 



(a) A maxillary surface, applied to the maxilla ; 



