THE CRAXIl'M. 165 



//-,/ <(/,>; <l line. Above this line there is often a second less distinctly marked 

 ridge, called the highest curved line (Unea supremo] ; to it the epicranial aponeurosis 

 is attached. The bone between these two lines is smoother and denser than the 

 rest of the surface. Running parallel with these from the middle of the crest is 

 another semicircular ridge on each side, the inferior curved lines. The surface of 

 the bone above the superior curved lines is rough and porous, and in the recent 

 state is covered by the Occipito-frontalis muscle, while the ridges, as well as the 

 surface of the bone between them, serve for the attachment of numerous muscles. 

 The superior curved line gives attachment internally to the Trapezius. externally 

 to the muscular origin of the Occipito-frontalis, and to the Sterno-cleido-mastoi'd 

 to the extent shown in Fig. 130 ; the depressions between the curved lines to the 

 Complexus internally, the Splenius capitis and Obliquus capitis superior exter- 

 nally. The inferior curved line and the depressions below it afford insertion to 

 the Rectus capitis posticus, major and minor. 



The foramen magnum is a large, oval aperture, its long diameter extending from 

 before backward. It transmits the medulla oblongata and its membranes, the 

 spinal accessory nerves, the vertebral arteries, the anterior and posterior spinal 

 arteries, and the occipito-axial ligaments. Its back part is wide for the transmis- 

 sion of the medulla, and the corresponding margin rough for the attachment of the 

 dura mater enclosing it ; the fore part is narrower, being encroached upon by the 

 condyles: it has projecting toward it. from below, the odontoid process, and its 

 margins are smooth and bevelled internally to support the medulla oblongata. On 

 each side of the foramen magnum are the condyles, for articulation with the atlas ; 

 they are convex, oblong, or reniform in shape, and directed downward and out- 

 ward : they converge in front, and encroach slightly upon the anterior segment of 

 the foramen. On the inner border of each condyle is a rough tubercle for the 

 attachment of the ligaments (check} which connect this bone with the odontoid 

 process of the axis ; whilst external to them is a rough tubercular prominence, 

 the ?/v///.v, ,/*. nv jugular process (the representative of the transverse process of a 

 vertebra), channelled in front by a deep notch, which forms part of the jugular 

 foramen or foramen lacerum posterius. The under surface of this process presents 

 an eminence which represents the paranuulotd process of some mammals. The 

 eminence is occasionally large, and extends as IOAV as the transverse process of the 

 atlas. This surface affords attachment to the Rectus capitis lateralis muscle and 

 to the lateral occipito-atlantal ligament ; its upper or cerebral surface presents a 

 deep groove which lodges part of the lateral sinus, whilst its external surface is 

 marked by a quadrilateral rough facet, covered with cartilage in the fresh state, and 

 articulating with a similar surface on the petrous portion of the temporal bone. On 

 the outer side of each condyle, near its fore part, is a foramen, the anterior con~ 

 '////"/'/ ; it is directed downward, outward, and forward, and transmits the hypo- 



<il nerve, and occasionally a meningeal branch of the ascending pharvngeal 

 artery. This foramen is sometimes double. Behind each condyle is a fossa, 1 some- 

 times perforated at the bottom by a foramen, the posterior condyloid, for the trans- 

 mission of a vein to the lateral sinus. In front of the foramen magnum is a strong 

 quadrilateral plate of bone, the basilar process, wider behind than in front; its 

 under surface, which is rough, presenting in the median line a tubercular ridge, 

 the pharyngeal ,/>///'. for the attachment of the tendinous raphe and Superior 

 constrictor of the pharynx : and on each side of it rough depressions for the 

 attachment of the Rectus capitis anticus. major and minor. 



The Internal or Cerebral Surface (Fig. 131) is deeply concave. The posterior 

 or occipital part is divided by a crucial ridge into four fossae. The two superior 



e receive the occipital lobes of the cerebrum, and present slight eminences 

 and depressions corresponding to their convolutions. The two inferior, which 

 receive the hemispheres of the cerebellum, are larger than the former, and com- 



1 This fossa presents many variations in size. It is usually shallow, and the foramen small ; occa- 

 sionally wanting on one or both sides. Sometimes both fossa and foramen are large, but confined to 

 one side only ; more rarely, the fossa and foramen are very large on both sides. 



