252 HEAD AND NECK 



anteriorly by its companion vein and the common carotid 

 artery. Numerous large sympathetic twigs accompany it. 



The vertebral artery on the left side is posterior to the 

 internal jugular vein and the common carotid artery, and it 

 is crossed by the thoracic duct. 



The vertebral vein issues from the aperture in the transverse 

 process of the sixth cervical vertebra. It passes downwards, 

 antero-lateral to its companion artery, and posterior to the 

 internal jugular vein, to open into the posterior aspect of the 

 commencement of the corresponding innominate vein. Near 

 its termination it crosses the subclavian artery. It receives 

 the deep cervical and the anterior vertebral veins. 



Truncus Thyreocervicalis (O.T. Thyroid Axis). This is 

 a short wide trunk, which arises from the anterior aspect 

 of the subclavian artery, close to the medial margin of the 

 scalenus anterior, and under cover of the internal jugular vein. 

 It lies between the phrenic and vagus nerves, and almost 

 immediately breaks up into its three terminal branches viz., 

 the inferior thyreoid, the transverse scapular, and the transverse 

 cervical. 



Arteria Thyreoidea Inferior. This vessel takes a sinuous 

 course to reach the thyreoid gland. At first, it ascends for 

 a short distance along the medial border of the scalenus 

 anterior, and under cover of the internal jugular vein ; then, 

 at the level of the cricoid cartilage, it turns suddenly medial- 

 wards and passes posterior to the sympathetic, the vagus, and 

 the common carotid artery, to the posterior border of the 

 thyreoid gland, where it gives off branches to the larynx and 

 then descends along the posterior border of the gland, dis- 

 tributing branches to its substance and to the trachea and the 

 oesophagus. 



The following branches will be noticed arising from the 

 inferior thyreoid artery : 



1. Ascending cervical. 5. CEsophageal. 



2. Inferior laryngeal. 6. Glandular. 



3. Tracheal. 7. Muscular. 



4. Pharyngeal. 



Arteria Cervicalis Ascendens. This small but constant vessel 

 runs upwards in the interval between the scalenus anterior 

 and longus capitis, and gives branches to the muscles in 

 front of the vertebral column. It also gives off spinal branches, 

 which enter the vertebral canal upon the spinal nerves, and 



