THE ANTERIOR THORACIC REGION. 



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ward to join the axillary fascia, and outward to join the fascia over the short 

 head of the Biceps. The costo-coracoid membrane is pierced by the cephalic vein, 

 the acromial thoracic artery and vein, superior thoracic artery, and anterior 

 thoracic nerves. 



The Pectoralis minor (Fig. 303) is a thin, flat, triangular muscle, situated at 

 the upper part of the thorax, beneath the Pectoralis major. It arises by three 



FIG. 303. Muscles of the chest and front of the arm, with the boundaries of the axilla. 



tendinous digitations from the upper margin and outer surface of the third, 

 fourth, and fifth ribs, near their cartilages, and from the aponeurosis covering the 

 Intercostal muscles ; the fibres pass upward and outward, and converge to form a 

 flat tendon, which is inserted into the inner border and upper surface of the cora- 

 coid process of the scapula. 



Relations. By its anterior surface, with the Pectoralis major and the superior 

 thoracic vessels and nerves ; by its posterior surface, with the ribs, Intercostal 

 muscles, Serratus magnus. the axillary space, and the axillary vessels and nerves. 

 Its upper border is separated from the clavicle by a triangular interval, broad 

 internally, narrow externally, bounded in front by the costo-coracoid membrane, 

 and internally by the ribs. In this space are the first part of the axillary vessels 

 and nerves. 



The costo-coracoid membrane should now be removed, when the Subclavius muscle will be 



seen. 



The Subclavius is a long, thin, spindle-shaped muscle, placed in the interval 

 between the clavicle and the first rib. It arises by a short, thick tendon from the 

 first rib and its cartilage at their junction, in front of the rhomboid ligament; the 



