14 ANATOMY. 



Describe their articulations, development, and muscles. Each parietal 

 bone articulates with 5 bones, the frontal, occipital, sphenoid, temporal, and 

 opposite parietal. It is developed from I centre in membrane. The only muscle 

 attached to it is the temporal. 



THE OCCIPITAL BONE. 



Describe its general features and surfaces. It is trapezoidal in form, 

 curved upon itself, and placed at the posterior and inferior region of the 

 cranium. Externally its surface is convex and presents for examination the 

 following, viz. 



External Occipital Protuberance, and Crest, for the attachment of the liga- 



mentum nuchse. 

 Superior and Inferior Curved Lines, extending outwards on each side of 



the external occipital crest. 

 Foramen Magnum, transmitting the medulla oblongata and its membranes, 



the vertebral arteries, and the spinal accessory nerves. 

 Condyles, 2 in number, for articulation with the atlas vertebra. 

 Tubercles, I on each condyle, for the check ligaments. 

 Anterior Condyloid Foramina, 2, for the hypoglossal nerves. 

 Posterior Condyloid Foramina, 2, (often absent) for veins. 

 Jugular Processes, 2, each helping to form the foramen lacerum posterius 



basis cranii. 

 Internally, the surface is concave, showing 



Fossa, 4, for the cerebellar and posterior cerebral lobes. 



Internal Occipital Protuberance, where 6 cranial sinuses meet to form the 



torcular (wine-press) Herophili. 



Crucial Ridge, the vertical portion for the falx cerebri and falx cerebelli ; 

 the transverse portion for the tentorium cerebelli, having also a groove for 

 the lateral sinus. 

 Groove, for the lateral sinus, and the inferior petrosal sinus, along the 



postero-lateral border. 



Internal Openings of the foramina described above. 



Describe the Basilar Process of the Occipital. It lies in front of the 



foramen magnum, articulates with the body of the sphenoid bone, smooth and 



grooved internally for the medulla oblongata and pons varolii, which lie upon 



it ; rough inferiorly for the attachment of muscles, and presenting the 



Pharyngeal Spine, for the attachment of the superior constrictor muscle of 



the pharynx and its tendinous raphe. 



Describe its articulations and development. The occipital articulates 

 with 6 bones, the 2 parietal, 2 temporal, sphenoid, and atlas. It is 

 developed by 4 centres, I each for the posterior part, the basilar process, 



