CLAVICLE. 



77 



from cancellated tissue in others. A vascular foramen usually pierces the 

 inferior surface of the spine, and others are to be found on the anterior 

 surface of the bone, near the neck. 



THE CLAVICLE. 



The clavicle or collar-bone extends transversely outwards, with an inclina- 

 tion backwards, from the summit of the sternum to the acromion process of 

 the scapula, and connects the upper limb with the trunk. 



It is curved somewhat like an italic /: the convexity of the internal 

 curve is directed forwards, and extends over two-thirds of the length of the 

 bone ; that of the outer curve looks backwards, and is most marked near the 

 outer fourth of the bone. 



The clavicle, towards its scapular end, is compressed and broad from 

 above downwards, but in the extent of its inner curve it is more or less 

 prismatic or cylindrical. In its description, four surfaces of the shaft may 

 be distinguished, together with the two extremities. 



Fig. 68. THE BIGHT Fig. 68. 



CLAVICLE. ^ 



A, from above ; B, from 

 below. 



1, sternal end ; 2, acromial 

 end ; 2', small facet for arti- 

 culation with the acromion ; 

 3, groove on the lower 

 surface for the subclavius 

 muscle ; 4, rough elevation 

 at the place of attachment 

 of the coraco-clavicular liga- 

 ments ; 5, rough depression 

 at the place of attachment 

 of the costo-clavicular or rhomboid ligament ; 6, in front, the mark of the attachment of 

 the pectoralis major ; 7, that of the deltoid muscle. 



The superior surface is broadest in its outer part ; it is principally sub- 

 cutaneous, but near the inner extremity presents a slight roughness, marking 

 the clavicular attachment of the sterno-cleido-mastoid muscle. The anterior 

 surface opposite the outer curve is a mere rough border, from which the 

 deltoid muscle takes origin, but in the inner half of its extent is broadened 

 out into an uneven space more or less distinctly separated from the inferior 

 surface, and giving attachment to the pectoralis major muscle. The posterior 

 surface is broadest at the inner extremity, and smooth in the whole extent of 

 the internal curvature ; but towards its outer extremity it forms a narrow 

 rough border which separates it from the superior surface, and gives 

 attachment to the trapezius muscle. On the inferior surface an elongated 

 roughness near the scapular extremity marks the attachment of the coraco- 

 clavicular ligaments ; extending inwards from this, over the middle third of 

 the bone, is a groove in which the subclavius muscle is inserted ; and near 

 the sternal end is a smaller rough depression, to which the costo-clavicular 

 ligament is attached. 



The internal extremity is the thickest part of the clavicle. It presents a 

 somewhat variably concavo-convex surface, somewhat triangular in form, 

 with its most prominent angle directed downwards and backwards. The 

 compressed external extremity is convex from before backwards, and articulates 

 by a small oval surface with the acromion. 



