ANATOMY IN A NUTSHELL. 513 



5. The internal openings for the anterior condyloid foramina and pos- 

 terior condyloid foramina are seen on each side of the foramen magnum. 



The basilar process of the occipital hone on its inner surface has a median 

 groove for the medulla and the pons, and on each side of this groove there is a 

 narrow groove which joins another groove from the petrous portion of the 

 temporal bone to receive the inferior petrosal sinus. 



The superior ancle is a point where the occipital hone meet- the two 

 parietal bones. This is the position of the posterior fontanelle. 



Each lateral angle is the point where the occipital hone meets the 

 posterior inferior angle of the parietal bone and the mastoid pail of the tem- 

 poral bone. 



The inferior angle (basilar process) joins the body of the sphenoid hone. 



The superior border passes from one lateral angle to the superior angle 

 and helps to form the lambdoid suture. 



The inferior border passes from the lateral angle to the inferior angle. 

 The upper part of this border joins the mastoid bone and the lower part joins 

 the petrous portion of the temporal bone. 



LESSON CLXXII. 



Ossification. — It has from four to eleven centers of ossification. 



Articulation. — It articulates with the two parietal, two temporal, sphe- 

 noid, and atlas, thus making six bones. 



Attachment of Muscles. — It has twelve pairs of muscles attached to it, 

 (1) those to the superior curved line are Occipitofrontal is of the frontal 

 region, Trapezius of the first layer of the back, and Stemo-cleido-mastoid of the 

 superficial cervical region. 



2. To the space between the curved lines are the Complexus of the 

 fourth layer of the back, Splenius capitis of the third layer of the hack, and 

 Superior oblique of the fifth layer of the back. 



3. Those attached to the lnferiok curved line and the space re- 

 twekn it and the foramen macnum are the Rectus capitis posticus major, 

 and Rectus capitis posticus minor of the fifth layer of the back. 



4. That attached to the transverse process is the Rectus capitis 

 lateralis of the anterior vertebral region. 



5. Those attached to the basilar process are the Rectus capitis anticus 

 major, and Rectus capitis anticus minor of the anterior vertebral region, and 

 the Superior constrictor of the pharynx of the pharyngeal region. 



Blood Supply.— Occipital, posterior auricular, middle meningeal, verte- 

 bral, and ascending pharyngeal arteries. 



Occipito-frontalis. Description.— This muscle consists of an anterior 

 portion called frontal, and a posterior portion called occipital, ami a third por- 

 tion which is between these two which is called the tendinous aponeurosis. 



Origin. The occipital portion arises from the outer two-thirds or one- 

 half of the superior curved line of th 'cipital hone ami the mastoid process of 



the temporal hone. The frontal portion arises from the I 'yramidalis nasi. 



