160 



Muscles of the Thorax. 



314. Muscles of the Thorax. First Layer. 



J/. pcctoraUs major. Orig. : Of the clavicular portion from the sternal 

 extremity of the clavicle ; of the sterno-costal portion from the anterior 

 surface of the sternum and the cartilages of the six upper true ribs 

 (Fig. 215), frequently also from the aponeurosis of the external oblique 

 muscle of the abdomen. Insert, by a flat tendon two inches broad: Into 

 the anterior bicipital ridge (Spinet tulerculi major is) of the humerus. (Depresses 

 the arm and draws it forwards.) 



