146 



OSTEOLOGY. 



which modify the development of the bone. They usually include the whole thickness 

 of the cranial wall, or they may only involve the outer or inner tables of the cranial 

 bones. They are most frequent in the region of the lambda and the lambdoid suture. 

 They occur commonly about the pterion, and in this situation are called epipteric bones 

 (Flower). By their fusion with one or other of the adjacent bones they here lead to the 

 occurrence of a fronto-squamosal suture. Their presence has also been noted along the 

 line of the sagittal suture, and sometimes in metopic skulls in the inter-frontal suture. 

 They are occasionally met with at the asterion and more rarely at the obelion. They 

 appear less frequently in the face, but their presence has been noted around the lacrimal 

 bone, and also at the extremity of the inferior orbital fissure, where they may form an 

 independent nodule wedged in between the great wing of the sphenoid, the zygomatic, and 

 the maxillary bones. 



OSSA FACIEI. 



The bones of the face, seven in number, comprise two maxillae, two palates, 

 two zygoma tics, with the mandible or lower jaw. 



'Frontal process 



Lacrimal groove 



The Maxillae. 



The maxillae, of which there are two, unite to form the upper jaw. Each 

 consists of a body, with which are connected four projections, named respectively 

 the zygomatic, frontal, alveolar, and palatine processes. 



The body (corpus) is of pyramidal form, and contains within it a hollow called 

 the maxillary sinus. It has four surfaces a facial or antero-lateral, an infra- 

 temporal or postero-lateral, an orbital or supero- lateral, and a nasal or medial 

 and four processes the malar, frontal, alveolar, and palatine. 



Surfaces. The facies anterior (antero-lateral surface) is confluent below with 

 the alveolar process. Above, it is separated from the orbital aspect by the 

 margo infraorbitalis (infra-orbital margin), whilst medially it is limited by the free 

 margin of the nasal notch, which ends below in the pointed spina nasalis anterior 

 (anterior nasal spine). Posteriorly it is separated from the infra-temporal surface by 



the inferior border of 

 the zygomatic process. 

 The facial aspect of the 

 bone is ridged by the 

 sockets of the teeth 

 (juga alveolaria). The 

 ridge corresponding to 

 the root pf the canine 

 tooth is usually the 

 most pronounced; med- 

 ial to this/ and over- 

 lying the roots of the 

 incisor teeth, is the 

 shallow incisive fossa, 

 whilst placed laterally, 

 3 J on a higher level, is 

 the deeper canine fossa, 

 the floor of which is 

 formed in part by the 

 projecting zygomatic 

 process. Above this, 

 and near the infra- 

 orbital margin, is the 

 infra -orbital foramen, 

 the external opening of the infra-orbital canal, which transmits the infra-orbital 

 nerve and artery. 



Anterior 

 nasal spine 



Canine fossa 



Tuberosity 



FIG. 157. THE RIGHT MAXILLA (Lateral View). 



