

THE CRANIUM. 



57 



the pharyngeal spine, 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. 24) is deeply concave. The posterior 

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

 fossre 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- 

 paratively smooth ; both are marked by slight grooves for the lodgment of arteries. 

 At the point of meeting of the four divisions of the crucial ridge is an eminence, 

 the internal occipital protuberance. It nearly corresponds to that on the outer 

 surface, and is perforated by one or more large vascular foramina. From this 

 eminence the superior division of the crucial ridge runs upward to the superior 

 angle of the bone ; it presents a deep groove for the superior longitudinal sinus, 

 the margins of which give attachment to the falx cerebri. The inferior division, 

 the internal occipital crest, runs to the posterior margin of the foramen magnum, 



Superior angle. 



Inferior angle. 

 FIG. 24. Occipital bone. Inner surface 



on the edge of which it becomes gradually lost ; this ridge, which is bifurcated 

 below, serves for the attachment of the falx cerebelli. It is usually marked by a 

 single groove, which commences at the back part of the foramen magnum and 

 lodges the occipital sinus. Occasionally the groove is double where two sinuses 

 exist. The transverse grooves pass outward to the lateral angles ; they are deeply 

 channelled, for the lodgment of the lateral sinuses, their prominent margins afford- 



