324 A MANUAL OF ANATOMY 



Scapular Anastomoses Proper. — The arteries which take part in 

 these anastomoses are (i) the suprascapular and posterior scapular, 

 representing the subclavian; and (2) the dorsalis scapulae of the 

 subscapular, representing the third part of the axillary. The 

 suprascapular is a branch of the thyroid axis of the first part 

 of the subclavian, and the posterior scapular arises from the 

 transverse cervical, which is also a branch of the thyroid axis. 

 The suprascapular is distributed to the supraspinous and infra- 

 spinous fossae and venter, and so also is the posterior scapular. 

 The subscapular is distributed by its dorsalis scapulae branch to 

 the infraspinous fossa and venter. In the supraspinous fossa the 

 suprascapular anastomoses with the posterior scapular. In the 

 infraspinous fossa the suprascapular anastomoses with the dorsalis 

 scapulae, as does also the posterior scapular. In the venter of 

 the bone the ventral branches of the suprascapular and posterior 

 scapular anastomose with the ventral branch of the dorsalis 

 scapulae. At the lower angle of the bone the posterior scapular 

 anastomoses with the descending or teres branch of the dorsalis 

 scapulas. 



Acromial Anastomosis. — The arteries which take part in the 

 acromial anastomosis or rete on the upper surface of the acromion 

 process are as follows : (i) the supra-acromial branch of the supra- 

 scapular ; (2) branches of the acromio-thoracic artery of the first 

 part of the axillary ; and (3) a branch of the posterior circumflex of 

 the third part of the axillary. 



The importance of the scapular anastomoses comes into play after 

 ligature of the subclavian artery in the third part of its course. 



THE ARTICULATIONS OF THE CLAVICLE. 



Sterno - clavicular Joint. — ^This joint belongs to the class di- 

 arthrosis, and to the subdivision arthrodia. The articular surfaces 

 are the inner end of the clavicle and the clavicular impression on the 

 upper border of the presternum. The articular surface of the 

 clavicle is of larger size than that on the presternum, and the two 

 are separated by an interarticular fibro-cartilage. The joint is 

 surrounded by a complete capsule, which is weak above and 

 below, but strong in front and behind, where it constitutes the 

 anterior and posterior sterno-clavicular ligaments. Besides these 

 there are the interclavicular and costo-clavicular or rhomboid 

 ligaments. 



The anterior sterno-clavicular ligament is broad, and its fibres 

 extend obliquely downwards and inwards from the front of the 

 clavicle to the front of the presternum. The sternal head of 

 origin of the sterno-cleido-mastoid is in contact with it. The 

 posterior sterno-clavicular ligament resembles the anterior, and is 

 similarly disposed behind the joint. The sterno-hyoid muscle 



