70 



SPECIAL ANATOMY OF THE SKELETON 



THE CEREBRAL CRANIUM (CRANIUM CEREBRALE) (THE CALVARIA). 

 The Occipital Bone (Os Occipitale). 



The occipital bone is situated at the back part and base of the cranium, is curved 

 on itself, and is trapezoidal in shape. The bone presents for examination two 

 surfaces, four borders, and four angles. 



Surfaces. The external surface is convex. Midway between the summit 

 of the bone and the posterior margin of the foramen magnum a large oval 

 opening for transmission of the spinal cord is a prominent tubercle, the external 

 occipital protuberance (protuberantia occipitalis externa), and, descending from it 



Linea 

 suprema 



SUPERIOR 

 CONSTRICTOR 



of Pharynx. 



Fvz. 39. Occipital bone. Outer surface. 



as far as the foramen, a vertical ridge, the external occipital crest (crista occipitalis 

 externa). This protuberance and crest give attachment to the ligamentum 

 nuchse, and vary in prominence in different skulls. Passing outward from the 

 occipital protuberance is a semicircular ridge on each side, the superior curved 

 line (liuea nuchae superior}. Above this line there is often a second less distinctly 

 marked ridge, called the highest curved line (linea nuchae suprema); 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 

 line (linea nuchae inferior}. The surface of the bone above the linea suprema is 

 rough and porous, and in the recent state is covered by the Occipitofrontalis 

 muscle. The superior and inferior curved lines, together with the surfaces of 

 bone between and below them, serve for the attachment of several muscles. 



