r,2 THE SKELETOX 



the outer anil a lart^e portion of tlie lower wall and inferior circumference of the 

 orbit. The inferior is continuous with the zygoma, and gives origin to. the 

 anterior fibres of the masseter. The anterior border is in relation with the maxilla, 

 and near the margin of the orbit gives origin to a portion of the levator labri superi- 

 oris. The posterior border extends from the frontal to the zygomatic process, and 

 presents a doul)l(' curve; it gives attachment to the temporal fascia. This Ijorder 

 is directly continuous below with the upi)er border of the zygoma, and above with 

 the temporal ridge. 



Articulations. — The malar articulates with the maxilla, frontal, sphenoid, and 

 temporal l)ones. 



Blood-supply, — The arteries of the malar are derived from the infraorl)ital, 

 lachrymal l)ranches of the ophthalmic, transverse facial, and deep temporal arteries. 



The muscles connected with it are: — 



Zygomaticus major. Zygomaticus minor. 



Levator lal;)ii superioris. Masseter. 



Ossification. — The malar is a membrane-bone, and arises from two and occa- 

 sionally three centres, which appear in the eighth week of embryonic life, and 

 grow with astonishing rapidity: the bone quickly attains a relatively large size. 



Occasionally the two primary nuclei fail to coalesce, and the bone is represented 

 in the adult by two portions separated by a horizontal suture. Such bipartite 

 malars have been observed in skulls obtained from at least a dozen different races 

 of men. Bipartite malars have been seen with the suture vertical. That the bone 

 may arise from three centres is shown by the fact that tripartite malars have been 

 observed. 



At birth the maxillary process reaches as far forwards as the outer Ixu-der of the 

 infraorbital canal; subsequently it may send a process over the canal. 



TRE APPENDICULAR ELEMENTS OF THE SKULL 



The bones which form this group are the mandible (lower jaw), malleus, incus, 

 stapes, hyoid, the styloid process of the temporal bone, and the internal pterygoid 

 process of the sphenoid. 



THE MANDIBLE OR LOWER JAW 



The mandible (lower jaio or inferior maxilla) is in shape like a horseshoe; it con- 

 sists of a horizontal portion or body, and two vertical portions or rami. 



The body consists of a right and a left half, meeting in the middle line to form 

 the symphysis. Each lialf presents two surfaces and two borders. The external 

 surface is smooth and generally convex, and presents the following points of 

 interest: — The symphysis ends inferiorly in a triangular surface which forms the 

 chin. Near the symphysis is the incisive fossa, from which the levator menti 

 arises; external to this is the mental foramen through which the mental nerve 

 and artery issue. This foramen is in a line with the second bicuspid tooth. Ex- 

 tending backwards and u})wards from the mental protuberance, so as to become 

 continuous with the anterior border of the coronoid process, is the external oblique 

 line ; along its up])er l)order the depressor lahii infcrloris and depressor anguli oris 

 arise. The internal surface presents, at a point corresponding to the symphysis, 

 two ])airs of genial tubercles. The upper pair give origin to the genio-hi/o-glossi, 

 and the lower ])air afford insertion to the r/enio-hyoid nmscles. The tubercles occa- 

 sionally form a single, median, irregularly shaped eminence. By the side of 



