52 THE BONES OF THE HEAD. 



part of which is irregular, and fits against the anterior extremity of the lateral mass 

 of the ethmoid, completing the foremost cells of that bone ; in front of this the 

 surface is free in the outer wall of the nasal fossa, and in its lower part is crossed by 

 a smooth oblique ridge, called the agger nasi, which forms the upper boundary of 

 the atrial surface of the body. The anterior border is rough, often grooved, for 

 articulation with the nasal bone, and its summit is serrated for articulation with the 

 frontal. Posteriorly, it presents a continuation of the lachrymal groove, which has 

 already been seen on the nasal surface of the body, and which here lodges the lachry- 

 mal sac : the groove is bounded internally by a sharp linear edge, which articulates 

 with the lachrymal bone, and externally by a smooth border which forms part of the 

 orbital margin. 



The alveolar border or process, thick and arched, is hollowed out into sockets 

 or alveoli, corresponding in number, form, and depth to the roots of the teeth, which 

 are fixed in them. 



The malar process is thick and triangular : its anterior and posterior surfaces 

 are continuous with the facial and zygomatic surfaces of the body ; the superior is 



Fig. 52. FRONT PART OF THE PALATE AND ALVEOLAR ARCH OF AN 

 ADULT. | 



Showing the openings into the anterior palatine fossa. 1, 2, are 

 placed on the palate plates of the superior maxillary bones ; 4, anterior 

 palatine fossa, in which are seen four openings the two lateral, with 

 lines pointing to them from 1 and 2, are the incisor foramina ; the 

 anterior and posterior, indicated by 3 and 4, are the foramina of 

 Scarpa. 



rough and grooved to support the malar bone. The inferior border runs down on 

 the outer surface of the body in the form of a thick buttress opposite the first molar 

 tooth. 



The palate process or plate, along with that of the opposite side, forms about three- 

 fourths of the hard palate. Its superior surface is smooth, and concave from side to 

 side ; its inferior surface is vaulted and rough, and is marked laterally with grooves 

 for nerves and vessels, which reach the palate through the posterior palatine canal. 

 Its posterior extremity falls short of that of the alveolar arch and body of the bone, 

 and articulates with the horizontal plate of the palate bone, which completes the 

 hard palate. The mesial border, finely serrated, rises into a vertical ridge, which, with 

 its fellow, constitutes the nasal crest -a grooved elevation receiving the lower margin 

 of the vomer ; at the fore part this border rises suddenly to a considerable height, 

 and the more elevated portion is distinguished as the incisor crest ; forwards this is 

 prolonged into the anterior nasal spine, on its upper border rests the septal cartilage 

 of the nose, and into the angle behind it the truncated anterior extremity of the 

 vomer fits. Close by the side of the incisor crest on the upper surface of the palate 

 plate is seen a foramen which is directed downwards to the mouth, but in the lower 

 half becomes converted into a wider groove by deficiency of the inner wall. Thus, 

 when the two bones are placed in apposition, one orifice of considerable size is 

 formed on the palatal aspect, which divides above into right and left branches leading 

 to the corresponding nasal fossee ; the lower aperture is the anterior palatine fossa (or 

 canal), the lateral branches are the incisor foramina (or canals) or foramina of 

 Stensen. Farther, in the middle line are two other smaller foramina opening into 

 the anterior palatine fossa, one before, the other behind ; these are the foramina of 

 Scarpa. 



The incisor foramina are placed between the two elements, the premaxilla and the maxilla 

 proper, which make up the superior maxillary bone of human anatomy, and are the remains 

 of a primitive communication between the nose and mouth. In the lower animals they are 



