103 OSTEOLOGY. 



terminating externally in the external angular process at its junction with the 

 malar, and internally in the internal angular process ; towards the inner third of 

 this ridge is the supra-orbital notch or foramen, for the passage of the supra- 

 orbital vessels and nerve, and at its inner side a slight depression for the attach- 

 ment of the cartilaginous pulley of the Superior oblique muscle. Beneath the 

 supra-orbital ridge is the opening of the orbit, bounded externally by the orbital 

 ridge of the malar bone ; below, by the orbital ridge formed by the malar, supe- 

 rior maxillary, and lachrymal bones ; internally, by the nasal process of the supe- 

 rior maxillary, and the internal angular process of the frontal bone. On the outer 

 side of the orbit, is the quadrilateral anterior surface of the malar bone, perforated 

 by one or two small malar foramina. Below the inferior margin of the orbit is 

 the infra-orbital foramen, the termination of the infra-orbital canal, and, beneath 

 this, the canine fossa, which gives attachment to the Levator anguli oris ; bounded 

 below by the alveolar processes, containing the teeth of the upper and lower jaw. 

 Beneath the alveolar arch of the lower jaw are the mental foramen for the passage 

 of the mental nerve and artery, the external oblique line, and at the lower border of 

 the bone, at the point of junction of the body with the ram us, a shallow groove 

 for the passage of the facial artery. 



THE ORBITS. 



The Orbits (fig. 65) are two quadrilateral hollow cones, situated at the upper 

 and anterior part of the face, their bases being directed forwards and outwards, 

 and their apices backwards and inwards. Each orbit is formed of seven bones, 

 the frontal, sphenoid, ethmoid, superior maxillary, malar, lachrymal, and palate ; 

 but three of these, the frontal, ethmoid, and sphenoid, enter into the formation of 

 both orbits, so that the two cavities are formed of eleven bones only. Each cavity 

 presents for examination, a roof, a floor, an inner and an outer wall, a circumfer- 

 ence or base, and an apex. The Roof is concave, directed downwards and for- 

 wards, and formed in front by the orbital plate of the frontal ; behind, by the 

 lesser wing of the sphenoid. This surface presents internally the depression for 

 the fibre-cartilaginous pulley of the Superior oblique muscle ; externally, the 

 depression for the lachrymal gland, and posteriorly, the suture connecting the 

 frontal and lesser wing of the sphenoid. 



The Floor is nearly flat, and of less extent than the roof; it is formed chiefly 

 by the orbital process of the superior maxillary ; in front, to a small extent, by 

 the orbital process of the malar, and behind, by the orbital surface of the palate. 

 This surface presents at its anterior and internal part, just external to the lachry- 

 mal canal, a depression for the attachment of the Inferior oblique muscle ; exter- 

 nally, the suture between the malar and superior maxillary bones ; near its middle, 

 the infra-orbital groove ; and posteriorly, the suture between the maxillary and 

 palate bones. 



The Inner Wall is flattened, and formed from before backwards by the nasal 

 process of the superior maxillary, the lachrymal, os planum of the ethmoid, and 

 a small part of the body of the sphenoid. This surface presents the lachrymal 

 groove, and crest of the lachrj^mal bone, and the sutures connecting the ethmoid, 

 in front, with the lachrymal, behind, with the sphenoid. 



The Outer Wall is formed in front by the orbital process of the malar bone ; 

 behind, by the orbital plate of the sphenoid. On it are seen the orifices of one 

 or two malar canals, and the suture connecting the sphenoid and malar bones. 



Angles. The superior external angle is formed by the junction of the upper and 

 outer walls ; it presents, from before backwards, the suture connecting the frontal 

 with the malar in front, and with the orbital plate of the sphenoid behind ; quite 

 posteriorly is the foramen lacerum anterius, or sphenoidal fissure, which transmits 

 the third, fourth, ophthalmic division of the fifth and sixth nerves, and the 

 ophthalmic vein. The superior internal angle is formed by the junction of the 

 upper and inner wall, and presents the suture connecting the frontal with the 

 hchrymal in front, and with the ethmoid behind. This suture is perforated by 



