AXILLARY SPACE 37 



finally anastomoses with some of the terminal twigs of the 

 posterior circumflex artery of the humerus. 



Vena Axillaris. The axillary vein has the same extent 

 as the artery. It begins at the lower border of the teres 

 major, as the proximal continuation of the basilic vein of the 

 arm, and it becomes the subclavian vein at the outer margin 

 of the first rib. At the lower margin of the subscapularis 

 it receives the two vtncz comites of the brachial artery, and 

 above the level of the pectoralis minor it is joined by the 

 cephalic vein. Its other tributaries correspond, more or 

 less closely, to the branches of the axillary artery. 



M. Subclavius. The subclavius is a small muscle which 

 lies immediately below the clavicle, enclosed between the 

 two layers of the costo-coracoid membrane. It takes origin, 

 by a short rounded tendon, from the superior surface of 

 the first costal arch, at the junction of the bone with the 

 cartilage, and the fleshy belly is inserted into the shallow 

 groove on the inferior surface of the clavicle. The nerve of 

 supply is derived from the fifth and sixth cervical nerves and 

 enters the posterior surface of the muscle. When the muscle 

 contracts it depresses the clavicle and draws it slightly 

 forwards. 



Dissection. When the subclavius has been examined it must 

 be divided horizontally, and when that has been done the costo- 

 clavicular ligament will be found behind the medial end of the 

 muscle. 



At this stage, with the assistance of the dissector of the head 

 and neck, the clavicular part of the sterno-cleido-mastoid muscle 

 must be detached from the superior border of the clavicle and 

 the sternal part of the muscle must be pulled towards the median 

 plane. 



Articulatio Sternoclavicularis. The sterno-clavicular joint 

 is a diarthrodial joint, formed by the sternal end of the 

 clavicle, the lateral part of the superior border of the 

 manubrium sterni, and the superior surface of the sternal 

 end of the cartilage of the first rib. It helps to increase 

 the range of the forward, backward, and upward movements 

 of the arm. The clavicle is attached to the sternum and the 

 first rib by a strong fibrous capsule. Within the capsule is an 

 articular disc which separates the joint cavity into two parts. 

 It is attached to the superior border of the sternal end of the 

 clavicle, to the superior surface of the first costal cartilage, and 

 to the anterior and posterior parts of the capsule. On the 



