116 OSTEOLOGY. 



it is crossed by a groove, often (25 per cent., Krause) converted into a foramen the 

 supraorbital notch or foramen. Through this there pass the supraorbital nerve and 

 artery. Sometimes (16 per cent., Loja) a series of grooves, radiating upwards and 

 laterally, indicate the course of the nerve (Dixon). Above the supraorbital margin 

 the character of the bone displays marked differences in the two sexes : in the male, 

 above the interval between the two medial angular processes, there is usually 

 a well-marked prominence, called the glabella ; from this the fulness extends 

 laterally above the supraorbital margin, varying in degree and extent, and forming 

 the elevations known as the arcus superciliares (superciliary arches). The pro- 

 minence of these naturally reacts on the character of the supraorbital margins, 

 which are thicker and more rounded in the male than in the female. Passing 

 upwards over the glabella, the remains of the suture which originally separated 

 the two halves of the frontal bone can usually be seen ; above this point all trace 

 of the suture is generally obliterated. 



Extending from the zygomatic process is a well-marked ridge, which 



Frontal tuberosities 



A 



Temporal surface ^-Temporal line 



^__ ..==, ^ -Superciliary arch 



Zygomatic process (O.T. 

 Lateral angular process)- ^ m 



^^ / \ ifP^BPB ^Glabella and remains of frontal suture 



Supraorbital notch IfMclj^^ Medial angular process 



' For articulation with nasal bone wj 



>. Frontal spine 

 Fio. 128. THE FRONTAL BONE (Anterior View). 



curves upwards and slightly medially, then, turning backwards, it arches 

 across the lateral aspect of the bone. This is the linea temporalis, which serves 

 to separate the anterior surface of the frontal portion of the bone from its 

 temporal aspect. The latter (facies temporalis) forms the floor of the upper and 

 anterior part of the temporal fossa, and serves for the attachment of the temporal 

 muscle. r 



Pars Orbitalis. The orbital part of the bone consists of two transversely 

 curved plates, each having the form of a sextant ; their medial edges, which are 

 irregular and formed of cellular bone, lie parallel to each other, and are 

 separated in their posterior half by the incisura ethmoidalis (ethmoidal notch), 

 in which the ethmoid bone is lodged. The edges of the notch on either side 

 are grooved in front and behind by the anterior and posterior ethmoidal foramina, 

 which are completed when the ethmoid is in situ. The anterior transmits the 

 anterior ethmoidal branch of the naso-ciliary nerve and the anterior ethmoidal 

 vessels ; the posterior, the posterior ethmoidal vessels and nerve. Anterior to the 

 ethmoidal notch is the nasal notch, from the centre of which the nasal process 

 projects downwards and forwards to terminate in the frontal spine, which lies 

 between, and articulates with the nasal bones and perpendicular part of the 



