THE FROXTAL 



47 



fissure, the remains of the metopic suture, -svhich indicates the line of union of 

 the two bones representing the Irontal in early life. On each side of this suture a 

 little Ijelow the centre is the frontal eminence. Below tlie eminences, separated 

 l)y shallow grooves, are tlie two converging superciliary ridges, which approach 

 each other in the median line to form the nasal eminence. The smooth space 

 l)ounded l)y the converging superciliaiy ridges is tlie glabella. Below these ridges 

 the hone presents the sharp supraorbital ridges which end internally at the 

 internal angular, and externally at tlie external angular processes. Each ridge 

 lias a narrow, deep supraorbital notch (sometimes a complete foramen) at the 

 junction of the inner Avitli tlie middle third. At the bottom of this notch or 

 foramen a small opening communicates with the diploe. The external angular 

 jtrocesses are prominent and articulate Avith the malar bones; from each process a 

 ridge extends upwards and Ijackwards, marking off the lateral aspect of the bone, 

 where it assists in the formation of the temporal ridge and fossa. The internal 

 angular processes articulate with the lachrymal bones, and are separated by a 

 serrated interval, the nasal notch, wdiich receives the upper borders of the nasal 

 bones, and outside these the nasal processes of the maxillae. The notch has in the 

 middle a long pointed process, the nasal spine, which lies between the upper part 

 of the nasal bones and the mesethmoid. On each side of the spine an opening 

 leads into the large frontal sinuses. 



The under surfaces of the orbital plates are smooth and concave; they form the 



ARTICULATION WITH 

 NASAL BONE 

 ARTICUUTION WITH MAX- 

 ILLA 

 ARTICULATION WITH 

 LACHRYMAL 



ARTICULATION WITH OS 

 PLANUM 

 ARTICULATION WITH 



MALAR 

 ARTICULATION WITH 

 GREATER WING OF 

 SPHENOID 

 ARTICULATION WITH 

 LESSER WING OF 

 SPHENOID 



Fig. 57. — The Frontal Boxe. 

 nasal spine 



[Inferior view. 1 



TROCHLEAR FOSSA 



LACHRYMAL FOSSA 



— jRBITAL SURFACE 



ETHMOIDAL NOTCH 



roofs of the orbits. Each is sharply limited anteriorly by the sujDraorl lital ridge, 

 and presents at the outer angle the lachrymal fossa for the reception of the 

 lachrymal gland. Near the internal angle there is the small shallow supra- 

 trochlear fossa for the pulley of the superior obliqvie muscle. A sharp ridge runs 

 backwards from the internal angular process, and articulates successively with the 

 lachrymal and the os planum of the ethmoid. It has two notches, which are 

 converted into the anterior and posterior ethmoidal canals by articulation with the 

 OS planum. The posterior border of each orbital plate articulates with the lesser 

 wing of the sphenoid (orbito-sphenoid), and is continuous with a rough triangular 

 surface for the greater wing (ali-sphenoid). This triangular surface is continuous 

 anteriorly with the serrated malar ridge of the frontal, and, laterally, with that 

 border of the bone which articulates with the parietals to form the coronal suture. 

 Between the ethmoidal notch and the inner margin of the orljital surface there is 

 an irregular surface which forms the roofs of the ethmoidal cells. 



Articulations. — The frontal articulates with the parietal, sphenoid, ethmoid, 

 lachrymal, malar, maxilla, and nasal l)ones; with the epipterics when present, 

 and occasionally (as explained on page 38) with the squamosal, and with the 

 sphenoidal turbinal when it creeps into the orbit. 



It has the following muscles attached to it: — 



Corrugator supercilii. 

 Temporal. 



Occipito-frontalis. 

 Orbicularis palpebrarum. 



