THE OCCIPITAL BONE. 



173 



is separated by a suture, the petro-occipital, containing cartilage, from the petrous 

 portion of the temporal. 



Each condylar portion ' {exouipitai) presents on the inferior surface an oval 

 articular swelling, the condyle, which rests in the hollow on the atlas. They are 

 placed on each side of the front half of the foramen magnum. The hind ends reach 

 almost precisely to the middle of the aperture, and anteriorly they extend to the line 

 of the anterior border, their long axes converging in front. The articular surface, 

 which is convex in the line of the long axis, faces downward and outward. The curve 

 it presents varies greatly. In some cases it is nearly regular, in others the front and 

 back halves almost meet at an angle. There is usually a constriction of the articular 

 surface at the middle, where it may be crossed by a groove or a ridge. On the thick 

 inner border of each condyle is a tubercle for the odontoid ligament. Behind the 

 condyle is 2i fossa, into which usually opens the inconstant posterior condyloid fora- 

 7ne7i,'^ transmitting a vein. In front of the base of the condyle at its outer border is 

 the constant anterior condyloid fo?-ainen^^ the termination of a canal, from five to ten 

 millimetres long, which pierces the bone above the condyle and transmits the hypo- 



FiG. 192. 



Highest curved line 

 Superior curved line 



Inferior curved line s ^ 'j^ ^rf- 



Condyle 



Jugular process 



Jugular notch 

 Pharyngeal tubercle 



External occipital protuberance 



Trapezius 



Complexus 



Occipitahs 



Sterno-mastoideus 



Red. capit. post, 

 minor 



Splenius 

 Red. capit. post, 

 major 



Obliqttus superior 



Posterior condyloid fora- 

 men 

 Red. capit. lateralis 



Anterior condyloid foramen, probe in canal 



Red. capit. antic, minor 

 Superiii^ constrictor 



Red. capit. antic, major 



Occipital bone, external surface, from below. 



glossal nerve and, usually, a branch from the ascending pharyngeal artery and vein 

 or veins. It is sometimes divided into two. The bone projects outward from the 

 condyle as the Jugular process,^ which is enlarged at its outer end where it cobssihes 

 with the petrous portion of the temporal. This enlargement, moreover, extends 

 downward as the paroccipital process, which shows its greatest development in odd- 

 toed ungulates. In man it is usually very small, but it may be large and, very rarely, 

 join the atlas. The concave front of the jugular process and the bone extending 

 forward on its inner side form the Jugular notch ^ which bounds the posterior lacer- 

 ated foramen ® behind and internally. This is completed by the temporal bone. A 

 very small point, the anterior Jugular process, marks the front of the foramen. A 

 little behind this a larger though very delicate spine, the intrajugular process, 

 reaches across, marking off a small anterior part of the jugular foramen for the 

 passage of the ninth, tenth, and eleventh nerves from the larger one behind for the 

 lateral sinus. Sometimes the front of the jugular process is a smooth surface 

 bounded below by a ridge to which is attached the rectus capitis lateralis, and above 

 by a short border marking off a fossa on the upper surface of the bone ; occasionally 



' Pars lateralis. ^ CaDalis condyloideus. ^ Canalis bypoglossi. ■* Processus jugularis. ^ locisura jaenlaris. 

 juEulare. 



' Forameo 



