THE CLAVICLE. 175 



The shoulder is composed of the clavicle and scapula. It has 

 been supposed by some persons that the two last mentioned 

 bones belong properly to the thorax ; but upon examining the 

 motions of the upper extremity, it will appear that they fdrm an 

 essential part of it : and it is equally evident that they do not 

 contribute to the perfection of the thorax ; they are, therefore, 

 considered as a part of the upper extremity. 



The Clavicle^ 



Is the long crooked bone resembling the italic /, which is 

 placed almost horizontally between the upper lateral part of the 

 sternum and the acromion, or most prominent process of the 

 scapula which it keeps off from the trunk of the body. 



The clavicle, as well as other long bones, is larger at its two 

 ends than in the middle. The end next to the sternum is trian- 

 gular ; the angle behind is considerably protruded, to form a 

 sharp ridge, to which the transverse ligament, extended from one 

 clavicle to the other, is fixed. The side opposite to this is some- 

 what rounded. The middle of this protuberant end is irregularly 

 hollowed, as well as the cavity in the sternum for receiving it : 

 but, in a recent subject, the irregular concavities of both are 

 supplied by a movable cartilage ; which is not only much more 

 closely connected every where, by ligaments, to the circumference 

 of the articulation, than those of the lower jaw are, but it grows 

 to the two bones at both its internal and external end ; its sub- 

 stance at the external end being soft, but very strong, and 

 resembling the intervertebral cartilages. 



From its internal end, the clavicle, for about two-fifths of its 

 length is bended obliquely forwards. On the upper and front 

 part of this curvature a small ridge is seen, with a plane rough 

 surface before it ; whence the sterno-hyoideus and sterno-mas- 

 toideus muscles have in part their origin. Near the lower angle, 

 a small plane surface is often to be remarked, where the first 

 rib and this bone are contiguous, and are connected by a firm 

 ligament. From this a rough plane surface is extended outwards, 

 where the pectoral muscle has part of its origin. Behind, the 

 bone is made flat and rough by the insertion of the larger 



