THE CLAVICLE. 



257 



distinct, since the bursa appears to connect it with the capsule below and a thin 

 fascia with the clavicle above. 



The spino-glenoid ligament^ is an occasional little band at the great scapular 

 notch, running from the anterior border of the spine to the posterior edge of the 

 glenoid cavity, crossing the suprascapular vessels and nerve. 



THE CLAVICLE. 



The function of the clavicle,^ or collar-bone, which extends from the top of the 

 sternum to the acromion, is to give support to the shoulder-joint in the wide and 

 varied movements of the arm. It is found in mammals that climb, fly, dig, or swim 

 with movements requiring an outward and backward sweep of the arm. It is 

 absent in those that use the fore-limb simply for progression with movements nearly 

 restricted to one plane. It is present, but imperfectly developed, in some carnivora 



Fig. 275. 



Trapezius 



ACROMIAL END 



Right clavicle, superior and posterior surfaces. 



STERNAL END 

 Pectoralis major 



whose arms serve, in part, for prehension. In man it has a doubly curved shaft, a 

 thick inner end, and a flattened outer one. 



The shaft is convex in front through the two inner thirds and concave in the 

 outer one. The former portion has a superior, an inferior, an anterior, and a pos- 

 terior surface ; but in the outer third the two latter surfaces narrow into borders. 

 The superior surface is smooth, except for a slight unevenness at the inner end, 



Fig. 276. 



Acromial facet 



Pectoralis major 



Sternal facet 



Slerno-hyoia 



Trapezoid ridge 



Conoid tubercle 



Right clavicle, anterior and inferior surfaces. 



giving origin to the clavicular head of the sterno-cleido-mastoid. The inferior sur- 

 face has near the inner end an oval 7'oughness, which may or may not be raised, 

 for the rhomboid ligament from the cartilage of the first rib. Beyond this is a longi- 

 tudinal groove, more marked near the outer end,' for the insertion of the subclavius 

 muscle. Outside of the middle, near the hind border (sometimes on the hind surface), 

 is the 7iutrient foramen, directed outward. The anterior surface narrows continu- 

 ally from within outward. The inner two-thirds are rough for the pectoralis major ; 



* Lie. transversum scapulae inferius. " Clavicula. 



17 



