156 



SPECIAL ANATOMY OF THE SKELETON 



of each side; at the sides, the innominate artery, the left common carotid, and 

 left subclavian arteries, the internal mammary and superior intercostal arteries, 

 the right and left innominate veins, the vagus, cardiac, phrenic, and sympathetic 

 nerves, the anterior branch of the first thoracic nerve, and the recurrent laryngeal 

 nerve of the left side. The apex of each lung, covered by the pleura, also projects 

 through this aperture, a little above the margin of the first rib. 



First thoracic 



,A (First lumbar 



FIG. 121. The thorax. Dorsal view. (Spalteholz.) 



The inferior or lower opening (apertura thoracis inferior) is formed by the 

 twelfth thoracic vertebra behind, by the twelfth ribs at the sides, and in front 

 by the eleventh, tenth, ninth, eighth, and seventh costal cartilages, which ascend 

 on either side and form an angle, the subcostal angle (angulus infrasternalis), 

 from the apex of which the ensiform cartilage projects. It is wider transversely 

 than from before backward. It slopes obliquely downward and backward, so 

 that the cavity of the thorax is much deeper behind than in front. The 

 Diaphragm ok i s in the opening forming the floor of the thorax. 



