240 



THE SKELETON. 



the two muscular impressions is a small subcutaneous interval. The posterior or 

 cervical surface is smooth, flat, and looks backward toward the root of the neck. 

 It is limited, above, by the superior border; below, by the subclavian border; 

 internally, by the margin of the sternal extremity ; externally, it is continuous 

 with the posterior border of the flat portion. It is concave from within outward, 

 and is in relation, by its lower part, with the suprascapular vessels. This surface, 

 at about the junction of the inner and outer curves, is also in close relation with 

 the brachial plexus and subclavian vessels. It gives attachment, near the sternal 

 extremity, to part of the Sterno-hyoid muscle ; and presents, at or near the middle, 

 a foramen, directed obliquely outward, which transmits the chief nutrient artery 

 of the bone. Sometimes there are two foramina on the posterior surface, or one 

 on the posterior, the other on the inferior surface. The inferior or subclavian 



Acromial extremity. 



Sternal extremity. 



FIG. 192. Left clavicle. Superior surface. 



surface is bounded, in front, by the anterior border ; behind, by the subclavian 

 border. It is narrow internally, but gradually increases in width externally, and 



FIG. 193. Left clavicle. Inferior surface. 



is continuous with the under surface of the flat portion. Commencing at the 

 sternal extremity may be seen a small facet for articulation with the cartilage of 

 the first rib. This is continuous with the articular surface at the sternal end of 

 the bone. External to this is a broad, rough impression, the rhomboid, rather 

 more than an inch in length, for the attachment of the costo-clavicular (rhomboid) 

 ligament. The remaining part of this sin-face is occupied by a longitudinal groove, 

 the subclavian groove, broad and smooth externally, narrow and more uneven 

 internally ; it gives attachment to the Subclavius muscle, and by its anterior 

 margin to the costo-coracoid membrane. Not unfrequently this groove is sub- 

 divided into two parts by a longitudinal line, which gives attachment to the inter- 

 muscular septum of the Subclavius muscle. 



The internal or sternal extremity of the clavicle is triangular in form, directed 

 inward and a little downward and forward ; and presents an articular facet, 

 concave from before backward, convex from above downward, which articulates 

 with the sternum through the intervention of an interarticular fibro-cartilage ; the 

 circumference of the articular surface is rough, for the attachment of numerous 



