THE HEAD AND NECK 1145 



artery. The inferior thyroid vein, which does not accompany the 

 corresponding artery, will be found described in connection with 

 the thyroid body. 



The transverse cervical and suprascapular veins return the blood 

 from the parts supplied by the corresponding arteries, and are 

 tributaries of the lower part of the external jugular vein. 



The deep cervical vein (posterior vertebral vein) commences in 

 the suboccipital venous plexus wdthin the suboccipital triangle. 

 It descends in company with the deep cervical artery, and passes 

 forvv'ards between the transverse process of the seventh cervical 

 vertebra and the neck of the first rib to terminate in the vertebral 

 vein. 



The anterior vertebral vein commences in a plexus in front of 

 the upper cervical transverse processes. It descends in company 

 with the ascending cervical branch of the inferior thyroid arter^', 

 receiving muscular tributaries in its descent, and it opens into the 

 lower part of the vertebral vein. 



Collateral Circulation after Ligation of the Third Part of the Sub- 

 clavian Artery. — (i) The suprascapular and the posterior scapular 

 branch of the transverse cervical, both branches of the thjToid 

 axis from the first part of the subclavian, take part in the scapular 

 anastomoses, and anastomose freely with branches of the first and 

 third parts of the axillary artery. (2) The internal mammary from 

 the first part of the subclavian anastomoses with the long thoracic 

 from the second part of the axillary. 



Collateral Circulation after Occlusion of the First Part of the 

 Subclavian Artery. — (i) The vertebral artery of one side anastomoses 

 with that of the opposite side. (2) The internal mammary anasto- 

 moses with the deep epigastric from the external iliac, and with 

 the aortic intercostal arteries. (3) The inferior thjToid anastomoses 

 with the superior thyroid from the external carotid. (4) The 

 superior intercostal anastomoses with the first aortic intercostal. 

 (5) The deep cervical of the superior intercostal anastomoses with 

 the deep branch of the ramus cervicalis princeps of the occipital 

 from the external carotid. (6) The scapular branches of the thyroid 

 axis anastomose with branches of the axillarj' artery. (7) The 

 thoracic branches of the axillary artery anastomose with the aortic 

 intercostals. 



Cervical Part of the Thoracic Duct. — ^This part of the thoracic 

 duct occupies the root of the neck on the left side, and lies upon 

 the side of the oesophagus, between the left common carotid 

 and left subclavian arteries. In this position it ascends to about 

 the level of the seventh cervical vertebra, and then it describes a 

 cune and passes outwards, forwards, and downwards in contact 

 with the dome of the left pleura. Thereafter it inclines inwards, 

 and, after receiving the left jugular and axillary- Ijonphatic trunks, 

 terminates in the angle of jimction of the intemaJ jugular and 

 subclavian veins of the left side. The terminal orifice of the duct 

 is guarded by a valve composed of two segments, which are so 



