ANATOMY IN A NUTSHELL. 511 



LESSON CLXXI. 

 The Occipital Bone. (Plates CCXLI-CCXLIL) 

 The occipital bone is situated at the posterior and inferior region of the 

 cranium and is trapezoidal in form. This bone is curved upon itself. 



The external surface is convex and has the following points for consideration : 



1. The external occipital protuberance is situated midway between 

 the superior point of the hone and the foramen magnum. It gives attachment 

 to the ligamentum nuchse. 



2. The external occipital crest is a vertical ridge extending from the 

 external occipital protuberance to the foramen magnum. Tins also gives at- 

 tachment to the ligamentum nucha?. 



3. The superior curved line extend- outward on each side from the 

 external occipital protuberance. This line gives attachment to the Trapezius 

 muscle internally and the Occipito-frontalis and Sterno-mastoid muscles ex- 

 ternally. 



4. The highest curved lixe (linea suprema) is above the superior curved 

 line and gives attachment to epicranial aponeurosis. 



5. The inferior curved lixe, which passes outward from the middle of 

 the external occipital crest together with a depression below it. gives attach- 

 ment to the Rectus capitis posticus major and Rectus capitis posticus minor. 



6. The depression between the superior and inferior curved lines gives 

 attachment to the Complexus muscle internally. Splenitis capitis and Superior 

 oblique externally. 



7. The foramen magnum is a large oval opening near the inferior angle. 

 Its greatest diameter is antero-posteriorly. It transmits the following struc- 

 tures: (a) the medulla and its membranes, (b) the spinal accessory nerve, (c) 

 the occipi to-axial ligaments, (d) vertebral arteries, (e) anterior and posterior 

 spinal arteries. 



8. The condyles are situated on each side of the anterior pail of the 

 foramen magnum. They are convex and reniform in shape. They look back- 

 ward and outward to articulate with the atlas. 



9. The tubercles are situated on the inner border of each condyle and 

 give attachment to the check ligaments. 



10. The jugulab processes (transverse) are situated externally to the 

 condyles, and help to form the posterior lacerated foramen. 



1 1 . The jugular foramen is on the anterior border of i lie jugular process. 



12. A quadrilateral facet is on the externa] surface of the jugular pro- 

 cess for its articulation with the petrous portion of the temporal bone. 



13. A deep <;k<><>\ e is on the upper surface of the jugular process for the 

 lateral sinus. 



14. Ax eminence (paramastoid in animals), which may extend to the 

 transverse process of the atlas, gives attachmenl to the Rectus capitis lateralis 

 muscle and the lateral occipito-atlantal ligament. 



1"). Anterior condyloid foramen is on the outer side of each condyle. It 



