32 



OCCIPITAL BONE. 



Fig. 9.* 



front of the foramen magnum 

 is the basilar process, grooved 

 on its surface, for supporting the 

 medulla oblongata ; and on each 

 side of the foramen a groove, 

 for the termination of the lateral 

 sinus ; a smooth surface which 

 forms part of the jugular fossa ; 

 and a projecting process which 

 divides the two and is called the 

 jugular eminence. Into the jugu- 

 lar fossa will be seen opening 

 the posterior condyloid foramen. 

 The superior borders are 

 very much serrated and assist 

 in forming the lambdoidal 

 suture; the inferior are rough, 

 but not serrated, and articu- 

 late with the mastoid portion 

 of the temporal bone by means 



of the additamentum suturae lambdoidalis. The jugular eminence 

 and the side of the basilar process articulate with the petrous por- 

 tion of the temporal bone, and the intermediate space, which is 

 irregularly notched, forms the posterior boundary of the jugular 

 foramen, or foramen lacerum posterius. ^ 



The angles of the occipital bone, are the superior, 1 * 'inferior, and 

 two lateral. The superior angle is received into the interval formed 

 by the union of the posterior and superior angles of the parietal 

 bones, and corresponds with that portion of the fcetal head which is 

 called the posterior fontanelle. The inferior angle is the articular 

 extremity of the basilar process. The lateral angles at each side 

 project into that interval formed by the articulation of the posterior 

 and inferior angle of the parietal with the mastoid portion of the 

 temporal bone. 



Developement. By four centres ; one (sometimes two) for the 

 posterior portion, one for each condyle, and one for the basilar pro- 

 cess. 



Articulations. With six bones; two parietal, two temporal, sphe- 

 noid, and atlas. 



Attachment of Muscles. To thirteen pairs ; to the rough surface 



* The internal surface of the occipital bone. 1. The left cerebral fossa. 2. The 

 left cerebellar fossa. 3. The groove for the posterior part of the superior longitudinal 

 sinus. 4. The spine for the falx cerebelli, and groove for the occipital sinus. 5. The 

 groove for the left lateral sinus. 6. The internal occipital protuberance which lodges 

 the torcular Hcrophili. 7. The foramen magnum. 8. The basilar process, grooved for 

 the medulla oblongata. 9. The termination of the groove for the lateral sinus, bounded 

 externally by the jugular eminence. 10. The jugular fossa ; this fossa is completed by 

 the petrous portion of the temporal bone. 11. The superior border of the bone. 12. 

 The inferior border. 13. The border which articulates with the petrous portion of the 

 temporal bone. 14. The anterior condyloid foramen. 



