no 



THE SKELETON 



deltoid tuberch', and gives origin to the deltoid muscle. Tlie posterior border is 

 thick and rounded; into it the trapezius is inserted. 



The inner two-thirds is prismatic in form; it has three surfaces and three 

 borders. Of these, the anterior surface is convex and presents near the 

 sternal end a rough surface for the clavicular portion of the pedoredis imijor, 

 and a rough surface above for the stenio-cleido-mastoid. Near the middle of 

 the shaft it is smooth and covered by the thin platysmn mijoides ; sometimes a 

 small canal passes at right angles through this surface of the clavicle; it is traversed 

 l)y a cutaneous l)ranch from the cervical plexus. The posterior surface is 

 concave, and forms an arch over the brachial plexus and subclavian artery. 



Fig. 118.— The Left Clavicle. (Superior surfiice.) 



AXTERIOr. 



Deltoid Peetoralis major 



Trapezius 



PusTKRIOR 



Sterno-mastoid 



The inferior surface commences externally as a groove for the subclavius, the 

 floor of the groove being continuous with the inferior surface of the outer third 

 of the clavicle, and frequently presents the orifice of the nutrient foramen. 

 Internally, this groove becomes very narrow, and runs on to the rough surface 

 for the rhomboid ligament. On the sternal side of the rhomboid impression 

 there is often a facet where the clavicle plays on the first costal cartilage. Near 

 this facet the sterno-Jn/oid muscle finds an attachment, and occasionally the sterno- 

 thyroid. Of the three borders, the superior separates the anterior and posterior 

 surfaces; it is faintly marked toAvards the sternal end; externally, it becomes 

 continuous with the posterior border of the outer third. The anterior border 



Fig. 119. — The Left Clavicle. (Inferior surface.) 

 Posterior 



Oblique 



line for 

 Capsular trapezoid Tuberosity for 

 ligament ligament conoid ligament 



Subolaviua 



Rhomboid 

 ligament and 

 Sterno- 

 hyoid Sterno-lbyroid 



FACET FOR FIRST 

 COSTAL CARTILAGE 



STERNAL FACET 



ACROMIAL FACET 



Peetoralis major 

 Anterior 



separates the anterior and inferior surfaces; it is continuous with the anterior 

 l)()rder of the flattened ])ortion. Tlie posterior border se))arates the inferior and 

 posterior surfaces, and forms the posterior lij) of the groove for the suhcliirius ; it 

 begins at the conoid tuljl'rcle, and ends at the rhomboid depression. The inner 

 or sternal end of the clavicle is broad and expanded; it ])laysupon a fibro-cartilage 

 interposed between it and the clavicular facet of the manubrium of the sternum, 

 and its borders are rough for the attachment of the sterno-clavicular and inter- 

 clavicular ligaments. The acromial, or outer end, presents a smooth articular 

 facet, directed slightly downwards for the acromion; its edges, especially the 

 superior, are rough for the attachment of the acromio-clavicular ligaments. 



