Thoracic Duct 157 



costal, and, in loose connective tissue, a little deeper, but in front of the 

 triangularis sterni, or pleura, is seen the artery with a vein on either 

 side. If the artery be tied in the second space, where the triangularis 

 sterni is not behind it, extra care must be given not to damage the 

 pleura in passing the aneurysm-needle. 



The superior intercostal artery descends from the second part 

 of the subclavian in front of the neck of the first and second ribs to 

 supply the topmost spaces, which the aortic intercostals cannot con- 

 veniently reach. The artery lies behind the apex of the pleura and 

 against the anterior division of the first dorsal nerve as it ascends 

 to the brachial plexus. Its intercostal branches anastomose with the 

 internal mammary and with thoracic branches of the axillary. 



It gives off theprofunda cervicis, which resembles the dorsal branch 

 of an aortic intercostal artery. Passing backwards between the seventh 

 cervical transverse process and the neck of the first rib, it eventually 

 ascends beneath the complexus, and anastomoses with branches of 

 the vertebral and with the princeps cervicis of the occipital (p. 30). 



Of the superior intercostal veins the right turns down into the great 

 azygos, whilst the left passes across the second part of the aortic arch 

 to end in the left innominate vein. 



The thoracic duct brings the chyle and lymph into the venous cir- 

 culation, with the exception of the lymph from the right side of head, 

 neck, and thorax, the right upper extremity, the right heart and lung, 

 and the phrenic surface of the liver. It is eighteen inches long, ex- 

 tending from the abdomen, through the thorax, and into the neck, to 

 the confluence of the left internal jugular and subclavian veins. 



It begins on the front of the second lumbar vertebra in the recep- 

 taculinn chyli, a dilatation into which is poured the contents of the 

 lymphatics of the lower extremities, pelvis and abdomen, and of the 

 lacteals. 



Relations. The duct is placed behind the abdominal aorta, and 

 between it and the right crus. It enters the posterior mediastinum 

 through the aortic opening, and ascends on the bodies of the dorsal 

 vertebrae, between the thoracic aorta and the great azygos. As it 

 is reaching the back of the transverse aorta it inclines towards the 

 left, and, passing behind the oesophagus, ascends between it and the 

 left subclavian artery. Having thus reached the root of the neck, it 

 arches downwards and forwards in the gap between the carotid and 

 subclavian arteries, to end in the confluence of the internal jugular 

 and subclavian veins, on a plane anterior to the arteries. 



At a post-mortem examination the duct is easily found, when the 

 pleura has been opened, by drawing the right lung towards the left, 

 and tearing through the parietal pleura along the right side of the 

 dorsal vertebrae. The duct is there lying in some loose connective 

 tissue between the great azygos and the oesophagus, whence it may be 

 traced upwards or downwards. 



