206 BONES OF THE FACE. 



is the maxillary process whicli articulates with, the maxil- 

 lary bone. 



From between these two processes the bone is smooth 

 and round, and forms about one third of the lower and 

 outer margin of the orbit. From this margin there projects 

 backwards into the cavity a thin plate of bone called the 

 internal orbital process. This process joins the sphenoid 

 and superior maxillary bones, and is notched posteriorly 

 where it bounds in front the spheno-maxillary fissure. The 

 lower margin of the cheek bone has the masseter muscle 

 attached, and from its posterior end proceeds the zygomatic 

 process, upon which rests a similar process from the tem- 

 poral bone. The internal or posterior surface is concave 

 and smooth, and forms part of the temporal fossa. The 

 structure is thick and cellular, having a delicate compact 

 covering. 



The development is from a single point of ossification, 

 commencing about the latter part of the second month. It 

 is articulated with four bones, i. e. frontal, sphenoid, tem- 

 poral, and superior maxillary. 



Lachrymal or Unguiform Bones, (pssa-unguis) The lach- 

 rymal or tear bones are two in number, and situated at 

 A. FIG. 47. B. the anterior and inner portion of the 

 orbit. Their form is oval, and present 

 an outer or orbital surface, which is 

 smooth and forms a portion of the in- 

 ner orbit. At the anterior part of this 

 surface is a vertical ridge, within which is a deep groove, to 

 unite with a corresponding one in the posterior part of the 

 nasal process of the superior maxillary, constituting the 

 upper portion of the nasal duct and lodging the lachrymal 

 sac. The internal or nasal surface is rough and covers the 

 anterior ethmoid cells. 



FIG. 47, A represents right side of os-unguis or Lachrymal Bone, upon the or- 

 bitar or outer aspect. 1 Upper margin. 2 Posterior margin. 3 Vertical ridge. 

 4 Inferior margin. 5 Anterior margin. 



FIG. 47, B represents the inner aspect of the same bone. 1245 Show 

 the same points as in A. The vertical groove is seen in this figure. 



