THE BONES OF THE HEAD 99 



The borders of the orbital surface are anterior, posterior, and 

 internal. The anterior border coincides with the infra-orbital 

 border. The posterior border, which has an inclination outwards, 

 forms the anterior boimdary of the spheno-maxillary fissure, and 

 presents a notch representing the commencement of the infra- 

 orbital groov^e. The internal border, antero-posterior in direction, 

 presents, behind the nasal process, the lachrymal notch for the 

 lachr\Tnal bone, and behind this it articulates, from before back- 

 wards, with the lower border of the os planum of the ethmoid and 

 the orbital process of the palate bone. This border presents a 

 few depressions which close in ethmoidal cells. 



The internal or nasal surface forms part of the outer waU of the 

 nasal fossa. It is limited in front by the mesial border of the 

 bone, behind by the posterior border, above by the internal 

 border of the orbital surface, and below for the most part by the 

 palatal process. It presents the opening of the antrum of 

 riighmore, in front of which is the deep lachrymal groove, directed 

 downwards, outwards, and backwards, and, after a course of 

 about ^ inch, opening into the front part of the inferior meatus 

 of the nose. This groove is converted posteriorly and internally 

 into the lachrymal canal by the lacluymal and inferior turbinate 

 bones, and it transmits the nasal duct. In front of the 

 lachrymal groove is a shghtly obhque ridge, called the inferior 

 turbinate crest, for articulation with the inferior turbinate bone, 

 and below this is a smooth concave siuface which forms the anterior 

 part of the inferior meatus-. Above the crest is the commencement 

 of another smooth surface, which extends upwards on to the inner 

 aspect of the nasal process, and forms the outer wall of the atritun 

 of the middle meatiis. Behind the opening of the antrum the 

 internal surface articulates with the perpendicular plate of the 

 palate bone, and it presents, from the centre downwards, a grocrs'^e, 

 directed downwards and fon^-ards, which, with the palate bone, 

 forms the posterior palatine canal for the great or anterior palatine 

 nerve, and the superior or descending palatine artery. Above the 

 opening of the antrmn are a few depressions on the internal border 

 of the orbital surface, forming ethmoidal cells. 



The nasal or frontal process ascends vertically from the mesial 

 part of the facial surface above the nasal notch. It is somewhat 

 triangular, and presents two surfaces and three borders. The 

 external surface is continuous with the facial surface of the body, 

 and gives attachment to the orbicularis palpebrarum, tendo ocuU, 

 and levator labii superioris alaeque nasi. The internal surface 

 forms part of the outer wall of the nasal fossa, and, at its back part 

 superiorly, it presents one or two depressions, completing cells 

 on the anterior border of the lateral mass of the ethmoid. The 

 surface is crossed obliquely backwards and upwards by a ridge, 

 called the agger nasi (mound) or superior turbinate crest, which 

 represents the naso-turbinal of most mammals (Schwalbe). This 

 crest boimds superiorly the atriima of the middle meatus, and 



