150 Anatomy Applied to Medicine and Sutgery. 



the right auricle, a small connecting branch uniting the 

 two vessels. The usual arrangement is for this connect- 

 ing branch to enlarge, and for the portion of the left vein 

 below it, to become obliterated, excepting at its termina- 

 tion in the heart, where it becomes the coronary sinus, 

 the obliterated portion being termed the vestigial fold of 

 Marshall. The superior vena cava, formed by the union 

 of the two innominates, is about two and a half inches in 

 length, and empties into the right auricle near the middle 

 of the sternum, on a level with the upper border of the 

 third left costal cartilage. The inferior vena cava brings 

 the blood from the lower half of the body, and, after 

 piercing the diaphragm and pericardium, enters the right 

 auricle. The azygos veins, right and left, arise in the ab- 

 domen from branches of the lumbar veins, and enter the 

 thorax, the right one through the aortic opening and the 

 left one in the substance of the left crus. These azygos 

 veins are situated in the posterior mediastinum and act, 

 as main' sewer veins, for the majority of the intercostal 

 spaces, but not for all of them, since the upper spaces 

 are drained by the superior intercostal veins. The 

 left veins cross about the level of the seventh' or eighth 

 dorsal vertebra and unite with the vena azygos major, 

 though occasionally, the left upper vein joins the left 

 superior intercostal. The vena azygos major arches over 

 the root of the right lung, and, after receiving the right 

 bronchial vein, empties into the superior vena cava just 

 before the latter vessel pierces the pericardium. 



Landmarks for the Veins. The left innomi- 

 nate vein may be represented by a line drawn across the 

 manubrium, from the left sterno-clavicular articulation, 

 to the lower border of the first costal cartilage on the right 

 side, about half an inch to the right of the sternum. Right 

 innominate vein, by a line starting at the upper border of 



