OSTEOLOGY. 35 



margin of the os nasi ; it is but half the length of the 

 inferior. The anterior margin slopes obliquely downwards 

 and forwards, and joins the posterior margin of the nasal 

 process of the anterior maxilla. It meets the inferior margin 

 at an acute angle in forming the posterior boundary of the 

 alveolar cavity for the tush. The posterior margin presents 

 an irregular concavity looking upwards. It is a rough 

 squamosal surface extending into the outer part of the bone, 

 increasing in width from above downwards, superiorly in ap- 

 position with the lachrymal, inferiorly with the malar bone. 

 This surface terminates above in a projecting point, which 

 slightly meets the squamous temporal bone. The inferior 

 surface of the projection is smooth for the passage of the 

 superior varicose vein of the face ; below, and slightly 

 behind, is an irregular prominence, tuberosity, to which 

 buccinator and retractor labii inferiosis are attached. The 

 inferior margin along the greater part of its length is occu- 

 pied by the alveolar cavities for the upper molars. These 

 consist of a series of deep square cavities, separating the 

 bone into two plates, and separated from one another by 

 thin bony septa. Their walls correspond to the external 

 surface of the teeth, into the grooves of which the bony 

 matter is moulded. They are six in number ; the first and 

 last cavities of the series are triangular, and sometimes at 

 the anterior angle of the first is a small alveolar cavity in 

 which the premolar or " wolf's tooth " is situated. In 

 front of this the inferior margin is smooth and rounded to 

 its anterior extremity. The external surface slopes obliquely 

 downwards and outwards. From about the centre of the 

 articulatory surface of the posterior margin (which en- 

 croaches considerably upon the surface) the anterior ex- 

 tremity of the zygomatic ridge runs forward for a short 

 distance. It terminates about opposite the second molar 

 tooth ; to its under surface are attached masseter externus 

 and zygomaticus, just in front of its anterior extremity 

 retractor labii superioris arises. Buccinator posteriorly and 

 caninus anteriorly arise from this surface just above the 

 inferior margin ; and between the former muscle and the 

 zygomatic spine is the superior varicose vein of the face. 

 The superior maxillary or infra-orhitar foramen is situated 

 above and in front of the zygomatic spine ; through it the 

 major portion of the dental branch of the superior maxillary 

 division of the fifth nerve (after passing through the 



