1 44 SKELETON. 



the lachrymal sac, is formed by the unusual breadth of the na- 

 sal process of the upper maxillary bone. In this case, the 

 only part of the os unguis which exists, is that in the same line 

 with the os planum. Several examples have come under my 

 own notice. Duverney has also mentioned it. Sometimes it 

 is entirely wanting, in which case the os planum joins the na- 

 sal process.* A variety still more uncommon is mentioned by 

 Verheyen, where the lachrymal fossa is formed exclusively by 

 the os unguis. 



This bone articulates very loosely with the adjoining bones, 

 so that it is frequently lost from the skeleton. It joins the os 

 frontis above, the os maxillare superius before and below, the 

 os planum behind, and the inferior spongy bone in the nose. 



5. Cheek Bones, (Ossa Malarum, Jugalia, Os de la Pommette.) 



These bones, two in number, are also called zygomatic by 

 many anatomists* They are situated at the external part of the 

 orbit of the eye, and form the middle external part of the face. 



The cheek bone is quadrangular, and has irregular margins. 

 It consists of two compact tables with but little intermediate 

 diploic structure. 



There are three surfaces to it.. That which contributes to 

 the orbit is crescentic, and is called the internal orbitar process. 

 The one in front is convex, and forms part of the face ; and be- 

 hind the latter is a third surface, which is concave, and forms a 

 part of the zygomatic fossa. Of the four margins, two are su- 

 perior, and two inferior. The anterior of the first two is con- 

 cave, and rounded off, to form the external and one-half of the 

 lower edge of the orbit. The posterior upper border above, 

 is thin and irregular, and to it is attached the temporal fascia: it 

 terminates behind by a short serrated margin, for articulating 

 with the zygomatic process of the temporal bone. The ante- 

 rior inferior margin, is serrated its whole length, for articulating 

 with the superior maxillary bone. The posterior inferior mar- 

 gin gives origin to part, of the masseter muscle. Some anato- 

 mists admit, also, a fifth margin to this bone, which is towards 

 the bottom of the orbit, and articulates above with the great 

 wing of the sphenoid bone, and below with the superior maxil- 



* Berlin, Traite D'Oatcol. vol. ii. p. 143. Paris, 1751. 



