MUSCLES OF THE UPPER EXTREMITIES. 205 



rior and posterior leaflet, except at the lower fourth of the 

 rectus, where the entire aponeurosis passes in front of the 

 muscle, with the aponeurosis of the transversalis making 

 the conjoined tendon of the transversalis and internal 

 oblique. 



The linea alba, or white line, extends along the 

 median line from the ensiform cartilage to the pubis. It 

 is formed by the union of the aponeuroses of the abdom- 

 inal muscles, and presents about its centre the umbilical 

 foramen for the transmission of the structures of the 

 umbilical cord in the foetus. In the adult it is obliter- 

 ated, the cicatrix being firmly adherent to the skin. The 

 linea alba is traversed by very few vessels and nerves. 

 The outer border of the rectus corresponds to the shallow, 

 semilunar grooves known as the semilunar lines. 



MUSCLES OF THE UPPER EXTREMITIES. 

 PECTORALIS MAJOR. 



Origin Inner half of clavicle, outer half of sternum, 



cartilages of true ribs. 



Insertion Passes upward and outward, and is inserted 

 into the anterior lip of the bicipital groove on the 

 humeras. 



Nerve Anterior thoracic, from brachial plexus. 

 PECTORALIS MINOR. 



Origin Anterior surface of third, fourth, and fifth 



ribs. 



Insertion Coracoid process of scapula. 

 Nerve Anterior thoracic, from brachial plexus. 



SUBCLAYIUS. 



Origin Cartilages of first rib. 



Insertion Under surface of the clavicle, about its 



centre. 

 Nerve Posterior thoracic of brachial plexus. 



