AXTERIOR ASPECT OF THE SKULL 73 



An elongated furrow, tlic scaphoid fossa, for the /^'//no/' j/^//*/// imisdc ;iii<l the 

 cartilage of the Eustachian tul»('. 



The general cavity of the pterygoid fossa which lodges the ten'^or palfifi and 

 iiiternal jttcrj/f/oid muscles. 



Frequently there is a notch in tlie external ])terygoid plate close heside the 

 foramen ovale. 



The posterior termination of the Vidian canal. 



If a line he drawn across the skuU-hase from one zygomatic tuhercle to the 

 other, it will fall immediately behind the external pterygoid plate and bisect 

 the foramen spinosum on each side. A second transverse line, drawn across the 

 opisthion or posterior margin of the foramen magnum, will fall behind the mastoid 

 j)rocesses. The space between these imaginary lines may be called the sub-cranial 

 region; that behind the second line the sub-occipital region. In addition to these 

 there is a lateral space anterior to the first line known as the zygomatic region. 

 Each will require se})arate consideration. 



The SUB-CRANIAL REGION is formed by the following bones: — In the centre, the 

 under surface of the bodies of the sphenoid and occipital l)ones. Laterally, the pe- 

 trosal, a small })iece of the greater wing of the sphenoid and of the squamosal, and 

 part of the ()ccii)ital. It i)resents the following points in the middle line for stud}': — 



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 he seen: — The anterior condyloid foramen for tlie hypo- 

 glossal nerve and a meningeal l)ranch of the ascending pharyngeal artery. 



The posterior condyloid fossa with the posterior condyloid foramen (this 

 foramen is not constant). 



The sphenotic (middle lacerated) foramen and the orifice of the Vidian canal. 



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

 tul)e. 



The carotid canal. 



Aqueductus 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 l)ranch of the ascend- 

 ing pharyngeal artery. 



The tympanic canaliculus for Jacobson's nerve. (Tynqianic of glosso- 

 pharyngeal. ) 



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



The glenoid fossa with the Glaserian fissure. This lodges the slender pro- 

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

 passage l)eside it, the canal of Huguier, conducts the chorda tympani nerve from 

 the tympanum. 



The external auditory meatus. 



Tlie auricular fissure for the tympanic branch of the vagus. 



The tympanic plate and vaginal ])rocess. 



Tlie styloid process. 



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

 facial nerve. 



The mastoid process Avith the digastric and occipital grooves. 



The SUB-OCCIPITAL REGION presents chiefly muscular ridges. They are the 

 superior, middle, and inferior nuchal lines, with the external occipital protuber- 

 ance and the external occipital crest. Behind the mastoid process is an opening 

 of varialile size, the mastoid foramen; a ])ranch of the occipital artery enters, and 

 a vein from tlie lateral sinus issues from this foramen. 



The ANTERIOR ASPECT of the skull is oval in outline, but presents a very irregular 

 surface. Its U])per portion, or forehead, presents the frontal eminences and 

 superciliary ridges. In the middle line is the prominence formed liy tlie nasal 

 hones, Avith a deep pyramidal recess, the orbits, on each side. Below the nasal 

 bones are the entrances to the nasal sinuses and the various recesses connected 

 with them. The teeth form a conspicuous feature in this view of the skull, the 

 outline of which is completed by the mandible. 



