108 THE SKELETON 



sphenoid. It is formed by the inferior surface of the basilar process of the 

 occipital and the body of the sphenoid, the petrous portion of the temporal bone, 

 a small piece of the squamosal portion, the posterior part of the great wing of the 

 sphenoid, and the condylar portions of the occipital bone. It presents the 

 follo-^dng points for examination (Figs. 95, 131): — 



The pharyngeal tubercle. 



The foramen magnum and the occipital condyles. The most anterior point of the foramen 

 is termed the basion, and the most posterior point the opisthion. 



On each side will be seen: — The hypoglossal foramen for the hypoglossal nerve and a men- 

 ingeal branch of the ascending pharyngeal artery. 



The condylar fossa with the condylar foramen (this foramen is not constant). 



The under aspect of the jugular process, from which the rectus capitis lateralis takes origin. 



The foramen lacerum and the orifice of the pterygoid (Vidian) canal. 



The canalis musculo -tubarius for the tensor tympani muscle and Eustachian tube. 



The carotid canal. 



The quadrilateral area for the origin of the levator veli palatini and tensor tympani muscles. 



The canaliculus cochleae, or ductus perilymphaticus. 



The jugular foramen and fossa for the glosso-pharyngeal, vagus, and spinal accessory 

 nerves, the internal jugular vein, and a meningeal branch of the ascending pharyngeal artery. 



The tympanic canaliculus for Jacobson's nerve (tympanic branch of glossopharyngeal). 



The spine of the sphenoid; this is sometimes fifteen millimetres in length. 



The mandibular fossa with the petro -tympanic fissure. This lodges the anterior process 

 of the malleus, the tympanic twig of the internal maxillary artery. A small passage beside 

 it, the canal of Huguier, conducts the chorda tympani nerve from the tympanum. 



The external auditory meatus. 



The auricular or tympano-mastoid fissure. 



The tympanic plate and vaginal process. 



The styloid process. 



The stylo-mastoid foramen for the stylo-mastoid artery and the exit of the facial nerve 

 and, in some cases, the auricular branch of the vagus. 



The mastoid process with the digastric and occipital grooves. 



(c) The suboccipital region is largely formed by the tabular portion of the 

 occipital bone with its ridges and areas for muscular attachment. Laterally a 

 small part of the mastoid portion of the temporal is seen, pierced by a small 

 foramen, of variable size, the mastoid foramen, which transmits a vein from the 

 transverse (lateral) sinus and a meningeal branch of the occipital artery. 



(5) The Anterior Region 



The anterior region {norma facialis) (figs. 132, 133) comprises the anterior 

 end of the cranium or forehead, and the skeleton of the face; also the cavities 

 known as the orbits, formed by the junction of the two parts of this region, and 

 the nasal fossae, situated on either side of the septum of the nose. 



The upper part or forehead, narrowest between the temporal crests about 

 half an inch above the zygomatic processes of the frontal, presents at this level 

 the two transverse sulci; above are the frontal eminences, below the superciliary 

 arches, and still lower the supra-orbital margins, interrupted near their medial 

 ends by the supra-orbital notches. 



Below the forehead are the openings of the orbits, bounded laterally by the 

 zygomatic bones constituting the prominences of the cheeks, and between them 

 the bridge of the nose, formed by the nasal bones and the frontal processes of the 

 maxilhe. Below the nasal bones is the apertura piriformis or anterior nasal 

 aperture, leading into the nasal fossse. The teeth form a conspicuous feature 

 in this view of the skull, the outline of which is completed below by the mandible. 



The bones entering into formation of the norma facialis are: — the frontal, nasals, lacrimals, 

 orbital surfaces of the small and the groat wings, and a portion of the body of the sphenoid, 

 the laminic papyracoa; of the cthmoids, the orl)ital processes of the palate bones, the zygomatics, 

 maxilla;, inferior nasal conchjc, and the mandible. 



The sutures are numerous, and for the most ])art .unimportant:— 



The transverse suture (fig. 1.33) extends from one zygomatic process of the frontal to the 

 other. The u|)pcr part of the suture is formed by tlu; frontal bone; below are the zygomatic, 

 great and small wings of the sphenoid, lamina papyracoa, lacrimal, maxillary, and nasal bones. 

 A portion of this complex suture, lying between the sphenoidal and frontal bones, appears in 

 the anterior cranial fo.ssa. 



Other fi.S3ures are the internasal, naso-maxillary, intor-maxillary and zygomatico-maxillary. 

 The small sutures seen in the orbit are (loscril)O(l with that cavity. 



The foramina are: — the supra-orl)ital, infra-orbital, optic, zygomatico-facial, and mental; 

 the naso-lacrimal canal; the ethmoidal canals; and the inferior and superior orbital fissures. 



