AXILLARY SPACE 



21 



cartilage. The deeper part arises by a variable number of 

 muscular slips from the cartilages of the upper six ribs. 



The muscle is inserted, by a flattened bilaminar tendon, 

 into the lateral lip of the intertubercular sulcus of the 

 humerus, and the fibres of the muscle undergo a rearrange- 

 ment as they converge upon the tendon. The greater 

 part of the clavicular portion joins the anterior lamina of the 

 common tendon ; some of the most medial clavicular fibres, 

 however, are inserted directly into -the humerus, distal to 

 the tendon, whilst a few gain attachment to the deep fascia 

 of the arm, and others become adherent to the adjacent 

 part of the deltoid. 



The fibres of the sternocostal portion of the muscle do 

 not all pass in the same direction but they all join the laminae 



Trapezoid 

 ligament 



Costo-clavicular ligament 



Conoid ligament 



FIG. 10. Inferior Surface of the Clavicle with the Attachments of the 

 Muscles mapped out. 



of the tendon of insertion. The superior fibres descend 

 slightly, the intermediate fibres pass horizontally, whilst the 

 inferior fibres ascend, and, at the same time, gain the deep 

 surface of the rest of the muscle. A smooth, full, and rounded 

 lower border of the muscle is thus formed \ it constitutes the 

 anterior fold of the axilla. The attachments of the muscle 

 to the humerus will be studied in detail at a later stage 

 of the dissection (p. 87). 



The pectoralis major is supplied by the medial and lateral 

 anterior thoracic nerves. It is an adductor of the superior 

 extremity and a medial rotator of the humerus. 



Axilla. The axilla is the hollow or recess between the 

 upper part of the side of the thorax and the proximal part 

 of the arm. When the arm is abducted from the trunk, 

 and the areolo-fatty tissue which occupies the axilla is 

 removed, the space disclosed has the form of a four-sided 

 pyramid. The apex, or narrow part of the space, lies 



