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A MANUAL OF ANATOMY 



posterior surface is concave over its inner two-thirds, and convex 

 over its outer third, where it is narrowed into a rough border. The 

 inner two- thirds overhang the subclavian vessels and trunks of 

 the brachial plexus, whilst the outer marginal third gives insertion 

 to the upper fibres of the trapezius. At the inner end of the im- 

 pression for these fibres, opposite the deltoid spine, there is a 

 conical projection which extends on to the inferior surface for a 

 little, called the conoid tubercle, for the conoid ligament. About 

 the centre of the posterior surface there is the medullary foramen 

 for the medullary artery, which is a branch of the suprascapular. 

 The canal to which the foramen leads is directed outwards. The 

 foramen may be situated on the inferior surface in, or close to, the 

 subclavian groove, or there may be two foramina, one on the 

 posterior and one on the inferior surface, about an inch apart. 



Rhomboid 

 Impression 



Trapezoid 

 Ridge 



Sternal 

 Articular Surface 



Fig. 99. — The Right Clavicle. 

 A. Inferior View ; B. Sternal Extremity. 



Close to the sternal end the posterior surface gives partial origin 

 to the sterno-hyoid. The inferior surface presents near its sternal 

 end the rhomboid impression, about an inch long, for the costo- 

 clavicular or rhomboid ligament. External to this there is the 

 subclavian groove, which extends from the rhomboid impression to 

 near the conoid tubercle, and gives insertion to the subclavius. 

 The groove is bounded by two lips, anterior and posterior, to which 

 the costo-coracoid membrane is attached in two laminae. At the 

 outer extremity of the inferior surface there is a rough oblique line, 

 called the trapezoid ridge, which extends forwards and outwards 

 from the conoid tubercle, and gives attachment to the trapezoid 

 ligament. The conoid tubercle is more fully seen here than on the 

 posterior border, and is situated at the postero-internal extremity 

 of the trapezoid ridge. 



The borders of the clavicle over its outer third are anterior and 

 posterior. The anterio/ border bifurcates, over the inner two-thirds, 



