12 THE UPPER EXTREMITY 



the pectoralis major and deltoid muscles, immediately below 

 the clavicle, are placed one, or it may be two, lymph glands 

 which receive the lymphatic vessels which accompany the 

 cephalic vein. These vessels convey the lymph from the 

 lateral side of the arm and the shoulder. 



M. Pectoralis Major. This powerful muscle extends from 

 the anterior aspect of the thorax to the humerus. It .is 

 divided by a deep fissure into a clavicular and a sternocostal 

 portion. The fissure" penetrates through the entire thickness 

 of the muscle, the clavicular and sternocostal portions being 

 thus distinct, except close to their insertion. The clavicular 

 portion arises by short tendinous and muscular fibres from an 

 impression on the medial half of the anterior surface of the 



Trapezoid 

 ligament 



Costo-clavicular ligament 

 Conoid ligament 



FIG. 5. Under Surface- of the Clavicle with the Attachments of the 

 Muscles mapped out. 



clavicle. The superficial part of the sternocostal portion takes 

 origin by fleshy fibres from the anterior surface of the sternum, 

 from the aponeurosis of the external oblique muscle, and, 

 occasionally, from the sixth rib near its cartilage. The deeper 

 part rises by a variable number of muscular slips from the 

 cartilages of the upper six ribs. 



The pectoralis major is inserted, by a flattened bilaminar 

 tendon, into the lateral lip of the sulcus intertubercularis of 

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

 arrangement as they converge upon this 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 below 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 take 



