140 



THE SKELETON 



foramen is situated on the inferior surface of the bone, in the subclavian groove. 

 On the inferior surface near the sternal end is a rough area, the costal tuberosity, 

 about three-quarters of an inch in length, for the attachment of the costo- 

 clavicular ligament, by which the clavicle is fixed to the first rib. More laterally 

 is a longitudinal groove for the subclavius, bordered by two lips, to which the sheath 

 of the muscle is attached. To the posterior of the two lips the layer of deep cer- 

 vical fascia which binds down the posterior belly of the omo-hyoid to the clavicle 

 is also attached. 



Of the three borders, the superior separates the anterior and posterior surfaces. Be- 

 ginning at the sternal end, it is well-marked, becomes rounded and indistinct in the middle, 

 whilst laterally it is continuous with the posterior border of the outer third. The posterior 

 border separates the inferior and posterior surfaces and forms the posterior lip of the subclavian 



Fig. 168. — The Left Clavicle. ■ (Superior surface.) 



Anterior 

 Deltoid Pectoralis major 



Epiphysial line 



Trapezius 



Posterior 



Sterno-mastoid 



groove. It begins at the costal tuberosity and can be traced laterally as far as the coracoid 

 tubercle, an eminence on the under aspect of the bone near the junction of prismatic and flat- 

 tened portions. The anterior border is continuous with the anterior border of the flattened 

 portion and separates the anterior and inferior surfaces. Medially, it forms the lower boundary 

 of the elliptical area for the origin of the pectoralis major, and approaches the posterior border. 

 Near the middle of the bone it coincides with the anterior lip of the subclavian groove. 



Flattened portion. — The lateral third of • the bone, extending from a point 

 opposite the coracoid process of the scapula to the acromial extremity, is flat- 



(Inferior surface.) 



Costo-clavicular 

 ligament and 

 sterno- 

 hyoid Sterno-thyreoid (occasional) 

 Facet for first 

 costal cartilage 



-Sternal facet 



Acromial facet 



Deltoid 



Anterior 



Pectoralis major 



tened from above downward and presents two surfaces and two borders. The 

 superior surface is rough and looks directly upward and gives attachment to the 

 trapezius behind and the deltoid in front; between the two areas the surface is 

 subcutaneous. On the inferior surface, near the posterior border, is a rough 

 elevation, the coracoid (conoid) tubercle; it overhangs the coracoid process and 

 gives attachment to the conoid ligament. From the coracoid tubercle, a promi- 

 nent ridge, the trapezoid or oblique line, runs laterally and forward to near 

 the lateral end of tlie bone. To it the trapezoid ligament is attached. The 

 conoid and trapezoid ligaments are the two parts of the coraco-clavicular liga- 

 ment which binds the clavicle down to the coracoid process. 



The anterior border is sharp, gives origin to the deltoid muscle, and frequently presents 

 near the junction of the flattened and prismatic portions a projection known as the deltoid 

 tubercle. The posterior border is thick and rounded, and receives the insertion of the upper 

 fibres of the trapezius. 



