THE NECK, ANTERIOR. Ill 



The second portion gives off the lateral spinal and mus- 

 cular branches to the contents of the spinal canal and 

 external spinal muscles. 



The Vertebral Vein. 



Begins in a plexus of small veins in the suboccipital 

 triangle, where it communicates with the intraspinal, deep 

 cervical, and occipital veins. It retraces the course of the 

 artery through the vertebral foramina, forming a venous 

 plexus about it in its course, appears at the foramen in the 

 sixth cervical vertebra, passes across the vertebral and 

 subclavian arteries, and opens into the innominate vein. 



Near its termination it is joined by the deep cervical 

 vein. See page 136. 



The Thyroid Axis. Fig. 1 8. 



This is a short trunk from the upper and front portion 

 of the first portion of the subclavian, at the inner border 

 of the scalenus anticus muscle. 



It breaks up into the inferior thyroid, transverse cervi- 

 cal, and suprascapular arteries. 



The Inferior Thyroid. Fig. 1 8. 



This is the largest branch of the axis. It takes a 

 winding course upward and inward to the lower border 

 of the thyroid gland. 



In its course it passes in front of the vertebral artery, 

 longus colli muscle, and the recurrent laryngeal nerve ; 

 and behind the internal jugular vein, pneumogastric nerve, 

 common carotid artery, sympathetic nerve cord and its 

 middle cervical ganglion (when that is present). 



Its branches are (a) muscular, to the adjacent muscles. 

 (b) Ascending cervical, which runs upward between the 

 vertebral attachments of the scalenus anticus and rectus 

 capitis anticus major, following up the phrenic nerve, sup- 



