ANTERIOR REGION OP THE SKULL. 185 



which indicate the situation of the frontal sinuses; and diverging from which 

 are the superciliary ridges which support the eyebrows. Beneath the nasal 

 eminences is the arch of the nose, formed by the nasal bones, and the nasal 

 processes of the superior maxillary. The nasal arch is convex from side to 

 side, concave from above downwards, presenting in the median line the inter- 

 nasal suture, formed between the nasal bones, laterally the naso- maxillary 

 suture, formed between the nasal bone and the nasal process of the superior 

 maxillary bone, both these sutures terminating above in that part of the trans- 

 verse suture which connects the nasal bones and nasal processes of the superior 

 maxillary with the frontal. Below the nose is seen the opening of the anterior 

 nares, which is heart-shaped, with the narrow end upwards, and presents late- 

 rally, the thin sharp margins serving for the attachment of the lateral cartilages 

 of the nose, and in the middle line below, a prominent process, the anterior 

 nasal spine, bounded by two deep notches. Below this is the intermaxillary 

 suture, and on each side of it the incisive fossa. Beneath this fossa is the 

 alveolar process of the upper and lower jaw, containing the incisor teeth, and 

 at the lower part of the median line, the symphysis of the chin, the mental 

 eminence, and the incisive fossa of the lower jaw. 



On each side, proceeding from above downwards, is the supraorbital ridge, 

 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 supraorbital. notch or foramen, for the passage of the supra- 

 orbital vessels and nerve, and at its inner side & slight depression for the 

 attachment of the 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, 

 superior maxillary, and lachrymal bones ; internally, by the nasal process of 

 the superior 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 infraorbital 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 jaw. Beneath the alveolar arch of the lower jaw is 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 ramus, a shallow groove for the passage of the facial artery. 



THE ORBITS. 



The Orbits (Fig. 132) are two quadrilateral pyramidal cavities, situated at tht, 

 upper and anterior part of the face, their bases being directed forwards and out- 

 wards, and their apices backwards and inwards. Bach 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 a outer wall, 

 four angles, a circumference or base, and an apex. The Roof'is concave, directed 

 downwards and forwards, 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 mus- 

 cle ; 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 surface 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 



