Inferior Maxilla 19 



The palate bone consists of a vertical and a horizontal part. The 

 former helps to close in the antrum and extends up into the floor of the 

 orbit. The horizontal part forms the back of the hard palate and of 

 the floor of the nose. Its under surface shows the ending of the pos- 

 terior palatine canal, and is also marked by a ridge for the attachment 

 of part of the tensor palati. To the posterior border is attached the 

 palatine aponeurosis, and from the posterior nasal spine arises the 

 azygos uvulae. 



The lachrymal, somewhat of the size and thickness of a finger- 

 nail, rests upon the inner border of the orbital plate of the maxilla, and 

 helps to fill in the anterior ethmoidal cells. Its upper border articu- 

 lates with the frontal, and its anterior with the nasal process of the 

 maxilla. A vertical ridge upon the orbital aspect of the bone marks 

 off a groove, which, with a groove upon the nasal process, lodges the 

 lachrymal sac and the upper part of the nasal duct (p. 76). The tensor 

 tarsi arises from the bone just behind the groove. 



The lachrymal bone is easily broken through in a clumsy attempt 

 to pass a style by the nasal duct, especially if the probe be held too 

 much in the horizontal position. 



The inferior maxilla. The outer surface of the body is marked 

 by an oblique line from which arise the muscles depressing the lower 

 lip and the angle of the mouth ; the platysma is inserted below this 

 line. The mental foramen is about half-way down the outer surface, 

 below the second bicuspid. The buccinator arises below the molar 

 teeth. 



The outer surface of the ramies is covered by the insertion of the 

 masseter, and near the anterior inferior corner of this muscle the bone 

 is grooved by the facial artery (p. 29). The levator menti arises in 

 the incisive fossa. 



An oblique ridge upon the inner surface of the body gives inser- 

 tion to the mylo-hyoid, and below it, running from the inferior dental 

 foramen, is the groove for the mylo-hyoid nerve and artery. 



Below the ridge also are the fossae for the sub-maxillary gland 

 and for the origin of the digastric, the latter being just behind the sym- 

 physis. Separated from the digastric fossa by the anterior part of 

 the mylo-hyoid ridge are the genial tubercles, and to the outer side of 

 the genial tubercles, above the mylo-hyoid ridge, is a slight depression 

 for the sublingual gland. The pterygo-maxillary ligament and the 

 superior constrictor are attached to the inner side of the body just 

 below and behind the last molar tooth. 



To the inner side of the angle the internal pterygoid is inserted, and 

 to the inner aspect of the coronoid process the temporal muscle. The 

 external pterygoid is inserted into the neck of the condyle. 



The lower jaw is developed in lateral halves, chiefly from the car- 

 tilage (Meckel's) of the first or the mandibular arch. The halves 

 have a fibrous connection at the symphysisat birth, but this is ossified 



