198 



OSTEOLOGY. 



of fibro-cartilage which is interposed between it and the clavicular facet on the 

 upper and lateral angle of the manubrium sterni. It is also supported by a small 

 part of the medial end of the cartilage of the first rib. Its articular surface, usually 

 broader from above downwards than from side to side, displays an antero-posterior 

 convexity, whilst tending to be slightly concave in a vertical direction. The edge 

 around the articular area, which serves for the attachment of the capsule of the 



ACROMIAL 

 ARTICULAR SURFACE 



TUBEROSITAS CORACOIDEA . 

 FIG. 184. THE EIGHT CLAVICLE SEBN FROM ABOVE. 



sterno-clavicular articulation, is sharp and well defined, except below, where it is 

 rounded. 



The body exhibits a double curve, being bent forwards in the medial two- 

 thirds of its extent, whilst in its lateral third it displays a backward curve. Of 

 rounded or prismatic form towards its sternal end, it becomes compressed 

 and flattened at its acromial extremity. It may be described as possessing two 

 surfaces, a superior and an inferior, separated by anterior and posterior borders, which 



are well defined towards the 

 lateral extremity of the bone, 

 but become wider and less 

 well marked medially where 

 they conform more to the 

 cylindrical shape of the bone.- 

 The superior surface, which is 

 smooth and subcutaneous 

 throughout its whole length, 

 is directed upwards and for- 

 wards. The anterior border, 

 which separates the superior from the inferior surface in front, is rough and tubercular 

 towards its medial end for the attachment of the clavicular fibres of the pectoralis 

 major, whilst laterally, where it becomes continuous with the anterior margin of 

 the acromial end, it is better defined, and bears the imprint of the origin of the 

 fibres of the deltoid muscle ; here, not uncommonly, a projecting spur of bone, 

 called the deltoid tubercle, may be seen. The posterior border is broad medially, 



FIG. 185. THE UPPER SURFACE OF THE RIGHT CLAVICLE 

 WITH MUSCLE ATTACHMENTS. 



TUBEROSITAS COSTALIS 



TUBEROSITAS CORACOIDEA 

 F IG> 186. THE EIGHT CLAVICLE SEEN FROM BELOW. 



where it is lipped superiorly to furnish an attachment for the clavicular fibres of the 

 sterno-mastoid muscle ; behind and below this the sterno-hyoid and sterno-thyreoid 

 muscles are attached to the bone. Laterally, the posterior border becomes more 

 rounded/and is confluent with the posterior edge of the acromial end at a point 

 where there is a marked outgrowth of bone from its inferior surface, the 

 tuberositas coracoidea. Into the lateral third 'of this border are inserted the 



