48 LACHRYMAL BONES. 



of separation between the facial and zygomatic surfaces, and pre- 

 sents a large triangular surface for articulation with the malar bone. 



The. .alveolar process forms the lower margin of the bone; it is 

 spongy and cellular in texture, and excavated into deep holes for 

 the reception of the teeth. 



The palate process is thick and strong, and projects horizontally 

 inwards from the inner surface of the body of the bone. Superiorly, 

 it is concave, and forms the floor of the nares ; inferiorly, it is also 

 concave, and assists in the formation of the roof of the palate. 

 Its internal edge is raised into a ridge, which, with a corresponding 

 ridge in the opposite bone, forms a groove for the reception of the 

 vomer. At the anterior extremity of its nasal surface is a foramen, 

 which leads into a canal formed conjointly by the two superior 

 maxillary bones, the naso-palatine canal. The termination of 

 this canal is situated immediately behind the incisor teeth, hence it 

 is also named the incisive foramen.* 



Developement. By six centres ; one for the body, one for each 

 of the three processes, nasal, malar, and palate ; and two for the 

 alveolar process. 



Articulations. With nine bones, viz. with two of the cranium 

 and with all the bones of the face, excepting the inferior maxillary. 

 These are, the frontal and ethmoid, nasal, lachrymal, malar, 

 inferior turbinated, palate, vomer, and with its fellow of the oppo- 

 site side. 



Attachment of Muscles. To nine ; orbicularis palpebrarum, obli- 

 quus inferior oculi, levator labii superioris alasque nasi, levator labii 

 superioris proprius, levator anguli oris, compressor nasi, depressor 

 labii superioris alseque nasi, buccinator, masseter. 



LACHRYMAL BONES (os unguis, from an imagined resemblance 

 to a finger nail). The lachrymal (fig. 23) is a thin oval-shaped 

 plate of bone, situated at the anterior and inner angle of the orbit. 

 It may be divided into an external and internal surface and borders. 

 The external surface is smooth and marked by a vertical ridge, 

 the lachrymal crest, into two portions, one of which is flat and 

 enters into the formation of the orbit, hence may be called the 

 orbital portion; the other is concave, and lodges the lachrymal 

 sac, hence the lachrymal portion. The internal surface is rough 

 and completes the anterior ethmoid cells, it assists in forming the 

 wall of the nasal fossse and nasal duct. 



Developement. By a single centre. 



Articulations. With /our bones; two of the cranium, frontal and 

 ethmoid; and two of the face, superior maxillary, and inferior 

 turbinated bone. 



Attachment of Muscles. To one muscle, the tensor tarsi, and to 

 an expansion of the tendo oculi, the former arising from the orbital 

 surface, the other being attached to the lachrymal crest. 



MALAR BONES (mala, the cheek). The malar (fig. 23) is the 

 strong quadrangular bone which forms the prominence of the 



* It contains a ganglion from the fifth pair. G. 



