THE ANTERIOR REGION OF THE SKULL. 113 



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 are the alveolar processes of the upper and 

 lower jaws, containing the incisor teeth, and at the lower part of the median line 

 the symphysis of the chin, the mental process, with its two mental tubercles, 

 separated by a median groove, and the incisive fossa of the lower jaw. 



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

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

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

 this ridge is the supraorbital notch or foramen, for the passage of the supraorbital 

 vessels and nerve. Beneath the supraorbital 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 and superior maxillary 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 infraorbital 

 canal, and beneath this the canine fossa, which gives attachment to the Levator 

 anguli oris ; still lower are the alveolar processes, containing the teeth of the upper 

 and lower jaws. Beneath the alveolar arch of the lower jaw is the mental foramen, 

 for the passage of the mental vessels and nerve, 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. 75) are two quadrilateral pyramidal cavities, situated at the . 

 upper and anterior part of the face, their bases being directed forward and 

 outward, and their apices backward and inward, so that the axes of the two, if 

 .continued backward, Avould meet over the body of the sphenoid bone. 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, four angles, a circumference or base, and an apex. The roof 

 is concave, directed downward and slightly forward, 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 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 directed upward and outward, and is 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 superior 

 surface of the orbital process of the. palate. This surface presents at its anterior 

 and internal part, just external to the lachrymal groove, a depression for the 

 attachment of the Inferior oblique muscle; externally, the suture between the 

 malar and superior maxillary bones ; near its middle, the infraorbital groove ; and 

 posteriorly, the suture between the maxillary and palate bones. 



The inner wall is flattened, nearly vertical, and formed from before backward 

 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 lachrymal bone, and the sutures connecting 

 the lachrymal with the superior maxillary, the ethmoid with the lachrymal in 

 front, and the ethmoid with the sphenoid behind. 



The outer wall is directed forward and inward, and is formed in front by the 

 orbital process of the malar bone ; behind, by the orbital surface of the greater 

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