THE MUSCULAR SYSTEM. .149 



LEVATORES COSTARUM. Twelve on either side. Origin, 

 from transverse processes of seventh cervical and eleven upper 

 dorsal vertebrae; insertion, into upper surface of the rib below, 

 between the angle and tubercle; action,, raises the ribs; nerve, 

 the intercostal. 



DIAPHRAGMATIC REGION. 



DIAPHRAGM. Origin, inner surface of ensiform cartilage, 

 cartilages and bony portions of six or seven lower ribs in front, 

 and from two aponeurotic arches, the ligamentum arcuatum ex- 

 ternum and internum and the lumbar vertebrae behind; inser- 

 tion, into the circumference of the central or cordiform tendon; 

 action, the principal muscle of inspiration and expulsion; nerves, 

 the phrenic, and phrenic plexus of the sympathetic. 



THE OPENINGS IN THE DIAPHRAGM. 



The aortic opening is placed posteriorly between the two 

 crura, in front of the spine. It transmits the aorta, thoracic 

 duct, and vena azygos major, and sometimes the left sympa- 

 thetic nerve. 



The cesophageal opening is in front of the decussation of 

 the crura, a little to the left and in front of the aortic opening. 

 It transmits the oesophagus and pneumogastric nerves. 



The foramen quaHratum, or opening for the vena cava, is 

 placed at the highest part of the central tendon, a little to the 

 right. It transmits the vena cava and maintains its patency. 

 The crus on each side transmits the sympathetic and greater and 

 lesser splanchnic nerves, and in addition the left transmits the 

 vena azygos minor. 



MUSCLES OF THE PERINEUM (vide PERINEUM). 



MUSCLES OF THE UPPER EXTREMITY. 

 MUSCLES OF THE SHOULDER. 



PECTORALIS MAJOR. Origin, from the sternal half of the 

 clavicle (clavicular portion) and anterior surface of the stern HIM 

 and costal cartilages from the second to the sixth or seventh 

 rib (sterno-costal portion) ; insertion, into the anterior bicipital 

 ridge of the humerus; action, draws the arm across the chest. 



PECTORALIS MINOR. Origin, upper and outer surface of the 

 third to the fifth rib, inclusive, and the aponeurosis of the inter- 

 costal muscles; insertion, into anterior border of the coracoid 

 process of the scapula; action, draws the scapula inward and 

 downward; nerve, the anterior thoracic. 



