Skull and Hyoid 



197 



the nasal processes of the two maxillae. The maxillae meet each other, not only on the 

 front, but also below, forming a large part of the hard palate ; this can be seen on 

 looking at the skull from below. Now look into the nasal cavity from the front : its 

 floor is evidently formed by the bony palatine processes of the maxillae, and a bony 

 septum is seen dividing the cavity into right and left. 



The outer margin of the orbital opening is not formed by the maxilla, but by the 

 malar which rests by a broad base on the maxilla and reaches to the external angular 

 process of the frontal above. Looked at from the side the malar is seen to throw a 

 process backwards and outwards to complete the zygomatic arch by joining the zygo- 

 matic process of the temporal : another part of the bone turns inwards and backwards, 

 forms the front wall of the temporal fossa, and articulates with the great wing of the 

 sphenoid. 



The orbital and nasal cavities can be more conveniently examined at a later 

 stage, but it is well to notice here that the mass of the ethmoid separates the 

 two orbits, the inner walls 

 of which are largely made by 

 the smooth os planum or side- 

 plate of the ethmoid. Being 

 in this situation the ethmoid 

 forms the upper part of the 

 nasal cavities, and its central 

 vertical plate is in the upper 

 part of the bony septum : the 

 lower and back part of the 

 septum is made by the vomer 

 which can be seen between the 

 posterior nasal openings, ar- 

 ticulating with the inferior sur- 

 face of the body of the sphe- 

 noid. The mass of the ethmoid 

 is placed against the front of 

 the body of the sphenoid. 



The nasal cavities, then, 

 lie not only between the maxillae 

 but at a higher level also, i.e., 

 between the orbits. This higher part is in the ethmoid, and a central vertical plate 

 of this bone divides the two cavities here, and articulates with the vomer below. 



Now turn the skull up and examine its under surface (Fig. 161), where we have seen 

 that the maxillae are joined below by palatine processes, which form the greater part 

 of the hard palate and floor of the nasal cavities. But behind these processes two 

 other smaller bones are seen completing the hard palate : these are portions of the 

 palate bones. It can be seen that the palatine process of each maxilla does not extend 

 back for the full depth of the bone, and the interval is filled by the palate. The palate 

 bone in its greater part is placed vertically against the internal aspect of the maxilla 

 in its back part, reaching down to the interval behind the palatine process ; here the 

 palate bone bends in at right angles to complete the bony palate ; it is thus divisible 

 into a vertical portion applied to the maxilla, and a horizontal part that helps to form the 

 palate. These general relations can be comprehended from a short study of the skull. 



But the palate bone also projects back further than the level of the maxilla, and 

 the posterior border of its vertical plate is applied to the front edge of the internal 



FIG. 164. Facial aspect, without lower jaw. 



