THE SUBCLAVIAN VESSELS. 595 



The <('/(> corresponding with the branches of the thyroid axis Veins 

 have the following destination : those with the suprascapular and 

 transverse cervical arteries open into the external jugular vein. But 

 the inferior thyroid vein, beginning in the thyroid body, descends 

 on the front of the trachea to the innominate vein. 



4. The superior intercostal artery arises from the posterior part of Superior 

 tlie subclavian under cover of the scalenus anticus on the right side and branch? 

 internal to the muscle on the left. It arches over the apex of the 

 lung, and passes downwards in front of the neck of the first rib ; its 

 distribution to the first two intercostal spaces has been seen in the 

 thorax (p. 483). 



Arising in common with this branch is the deep cervical artery, Deep 

 which passes backwards between the transverse process of the last branch, 

 cervical vertebra and the first rib, lying internal to the two hinder 

 i-aleni muscles and the fleshy slips continued upwards from the 

 erector spinse, to end beneath the complexus muscle at the posterior 

 part of the neck as already seen (p. 532). 



A spinal I/ranch is frequently given from the second part of the Spiual 

 subclavian artery ; its offsets are continued into the spinal canal branch> 

 through the intervertebral foramina. 



The SUBCLAVIAX VEIN is much shorter than the companion artery, Subclavian 

 reaching only from the outer edge of the first rib to the inner border ^ 

 of the anterior scalenus. It is a continuation of the axillary vein, 

 and ends by joining the internal jugular in the innominate trunk. 

 Its course is arched below the level of the artery, from which it is 

 separated by the scalenus anticus. 



Branches. The subclavian vein is joined at the outer edge of the its 

 anterior scalenus by the external jugular vein, and sometimes also 

 by the anterior jugular. Into the angle of union of the subclavian 

 and internal jugular veins the right lymphatic duct opens (fig. 215, 9 ) ; opening of 

 and at the like spot on the left side, the large lymphatic or thoracic d J ucts. ia ' 

 duct ends (fig. 215, 8 ). The highest pair of valves in the subclavian valves, 

 trunk is placed outside the opening of the external jugular vein. 



It should 1 >e borne in mind that occasionally the vein is as high Position 

 in the neck as the third part of its companion artery ; and that it may W1> ' 

 lias been seen in a few instances with the artery beneath the 

 anterior scalenus. 



The THORACIC DUCT conveys the chyle and lymph of the greater Thoracic 

 part of the body into the venous circulation. Escaping from the 

 thorax on the left side of the oesophagus, the duct ascends in the comes from 

 neck as high as the seventh cervical vertebra. At the spot men- 

 tioned it issues from beneath the carotid artery and the internal 

 jugular vein, and arches outwards and downwards above or over the 

 subclavian artery, and in front of the anterior scalenus muscle and and joins 

 phrenic nerve, to open into the angle of junction of the subclavian Ae 

 with the internal jugular vein. Double valves, like those of the valves; 

 veins, are present in the interior of the tube ; and a pair guards 

 the opening into the posterior part of the vein. Frequently the frequent 

 upper part of the duct is divided ; and there may be separate va 

 openings into the large veins corresponding with those divisions. 



QQ 2 



