54 



THE SKELETON 



from the lateral angle to the jugular process and articulates with the mastoid 

 portion of the temporal. 



The condylar or lateral portions [partes laterales] (ex-occipitals) form the 

 lateral boundaries of the foramen magnum and bear the condyles on their in- 

 ferior surfaces. The condyles are two convex oval processes of bone with smooth 

 articular surfaces, covered ^\\ih. cartilage in the recent state, for the superior 

 articular processes of the atlas. They converge in front, and are somewhat 

 everted. Their margins give attachment to the capsular ligaments of the 

 "bccipito-atlantal joints and on the medial side of each is a prominent tubercle 

 for the alar (lateral odontoid) ligament. The anterior extremities of the condyles 

 extend beyond the ex-occipitals on the basi-occipital portion of the bone. The 

 hypoglossal (anterior condyloid) foramen or canal [canalis hypoglossi] perforates 

 the bone at the base of the condyle, and is directed from the interior of the 

 cranium, just above the foramen magnum, forward and laterally; it transmits 

 the hypoglossal nerve and a twig of the ascending pharyngeal artery. 



The foramen is sometimes double, being divided by a delicate spicule of bone. Above the 

 canal is a smooth convexity known as the tuberculum jugulare sometimes marked by an obUque 

 groove for the ninth, tenth and eleventh cranial nerves. Post,er ior to, each con dyle is a pit, t he 



Fig. 67. 



-Cerebral Surface of the Occipital, Showing an Occasional Disposition of 



THE Channels. 



Torcular 



Vermiform fossa 



Condylar foramen 

 Hypoglossal foramen 



coadylar fossa, which receives the hinder edge of the superior articular pro cess of t he atlas when 

 th(! head is extended. The floor of the depression is occasionally perforated by^the condylar 

 (posterior condyloiTTj canal or foramen [canalis condyloideus], which transmits a vein from the 

 transverse sinus. Projecting hiterally opposite the condyle is a quadrilateral portion of bone 

 known as the jugular process, the extremity of which is rough for articulation with the jugular 

 facet on the petrous portion of the temporal bone. Up to twenty-five years the bones are united 

 here by means of cartilage; about this age ossification of the cartilage takes place, and the jugular 

 process thus becomes fused with the petrosal. Its anterior border is deeply notched to form the 

 posterior boundary of the jugular foramen, and the notch is directly continuous with a groove 

 on the upper surface which lodges the termination of the transverse sinus. In or near the groove 

 is .seen tin; inner opening of the condylar foramen. The lower surface of the process gives 

 attachment to the rectus capitis lateralin and the oblique occij)ito-atlantal ligament. Occa- 

 sionally the mastoid air cells extend into this process and rarely a process of bone, representing 

 the paramfiHtoid jtrncenn of many mammals, projects downward from its under aspect and may 

 be HO long as to join or articulate with the transverse process of the atlas. 



The basilar portion (basi-occipital) is a quadrilateral plate of bone projecting 

 forward and ui)ward in front of the foramen magnum. Its superior surface 

 presents a deep groove — the basilar groove [clivus]; it supports the medulla 

 oblf>ngata and gives attachment to the tectorial membrane (occipito-axial 

 ligament). The lower surface presents in the middle line a small elevation 

 known as the pharyngeal tubercle for the attachm(uit of the fibrous raph^ of the 

 pharynx, and iininediatcly in front of the tubercle there is freciuently a shallow 



