122 



OSTEOLOGY. 



The .posterior or subclavian border separates the posterior from the inferior 

 surface, and extends from the conoid tubercle to the rhomboid depression. It 

 forms the posterior boundary of the groove for the Subclavius muscle, and gives 

 attachment to the fascia which incloses it. 



The anterior surface is included between the superior and anterior borders. It 

 is directed forwards and a little upwards at the sternal end, outwards and still 

 more upwards at the acromial extremity, where it becomes continuous with the 

 upper surface of the flat portion. Externally, it is smooth, convex, nearly sub- 

 cutaneous, being covered only by the Platysma ; but, corresponding to the inner 

 half of the bone, it is divided by a more or less prominent line into two parts : an 

 anterior portion, elliptical in form, rough, and slightly convex, for the attachment 

 of the Pectoralis major; and an upper part, which is rough behind, for the 

 attachment of the Sterno-cleido-mastoid. Between the two muscular impressions 

 is a small subcutaneous interval. 



Fig. 82. Left Clavicle. Anterior Surface. 



Fig. 83. Left Clavicle. Inferior Surface. 



The posterior or cervical surface is smooth, flat, directed vertically, and looks 

 backwards towards 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 outwards, and is in relation, by its lower part, with the 

 suprascapular 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 outwards, which transmits the chief nutrient artery of the bone. Some- 

 times, there are two foramina on the posterior surface ; or one on the posterior, 

 the other on the inferior surface. 



The inferior or subclavian 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 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 or rhomboid ligament. The remaining part of this surface is occupied 

 by a longitudinal groove, the subclavian groove, broad and smooth externally, 



