176 THE CLAVICLE. 



share of the subclavian muscle. The clavicle is then curved 

 backwards, and at first is round ; but it soon after becomes broad 

 and thin ; which shape it retains to its external end. Along the 

 external concavity a rough sinuosity runs ; from which some part 

 of the deltoid muscle takes its rise : opposite to this, on the con- 

 vex edge, a scabrous ridge gives insertion to a share of the 

 trapezius muscle. The upper surface of the clavicle is here flat ; 

 but the lower is hollow, for lodging the beginning of the musculis 

 subclavius ; and towards its back part a tubercle rises ; to which, 

 and to a roughness near it, the strong, short, thick ligament, 

 connecting this bone to the coracoid process of the scapula, is 

 fixed. 



The external end of this bone is oblong horizontally, smooth, 

 sloping at the posterior side, and tipped in a recent subject with 

 a cartilage, for its articulation with the acromion scapulae. 

 Round this the bone is spongy, for the firmer connexion of the 

 ligaments. 



The surfaces of contact with this bone, and the scapula are 

 remarkably small, and flat also. 



The medullary arteries, having their direction obliquely out- 

 wards, enter the clavicles by one or more small passages in the 

 middle of their back part. 



The substance of this bone is the same as that of the other 

 round long bones. 



The ligaments which surround the articulation of this bone 

 with the sternum, are so short snd strong, that little motion can 

 be allowed any way ; and the strong ligament that is stretched 

 across the upper forcula of the sternum, from the posterior 

 prominent angle of the one clavicle to the same place of the 

 other clavicle, serves to keep each of these bones more firmly 

 in its place. By the assistance, however, of the movable inter- 

 vening cartilage, the clavicle can move at this articulation, so 

 that the external extremity may be elevated or depressed, and 

 moved backwards and forwards. The whole bone may be 

 moved so as to describe a cone ; of which the end at the sternum 

 is the apex. 



The movements of the scapula and arm are the objects of 



