136 



SPECIAL ANATOMY OF THE SKELETON 



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. 102) are two quadrilateral pyramidal cavities, situ- 

 ated 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, would rnepf over the body of the sphenoid bone. Each orbit 

 (orbita) is formed of seven bones the frontal, sphenoid, ethmoid. maxilla,, malar., 

 la.cri'mal. and palate: but three of these, the frontal r ethmoid, and sphenoid, 

 pnter 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 base, and an apex. 



TENDO OCULI 



Anterior nares 



Anterior- 

 nasal spine 



Incisive foss< 



\ Groove for 

 facial orten/ 



FIG. 102. Anterolateral region of the skull. 



The roof (paries superior} 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 carti- 

 laginous pulley of the Superior oblique muscle; externally, the depression for the 

 lacrimal gland; and posteriorly, the suture connecting the frontal and lesser wing 

 of the sphenoid. 



The floor (paries inferior) is directed upward and outward, and is of less extent 



