506 BLOOD-VESSELS OF THE NECK. 



the transverse process of the fifth or sixth, and sometimes 

 o^ the seventh cervical vertehra. It passes upward in the 

 "bony canal formed by the several foramina placed one above 

 another in the corresponding transverse processes, as high 

 as the dentata or second vertebra. Here it bends outward 

 and backward to the foramen in the transverse process of 

 the atlas, and then makes a very remarkable curve inward 

 and backward, round the articulation of the atlas, entering 

 the foramen magnum through the dura mater. It ascends 

 upon the medulla oblongata, and at the lower margin of 

 the pons, it unites with its fellow to form the basilar 

 artery. 



In the canal the vertebral artery sends out anterior, pos* 

 terior, and external branches, supplying the intertransver- 

 sales, complexus, splenius, rectus capitis anticus major, and 

 scaleni muscles ; while its internal branches go into the 

 spinal canal and supply the dura mater, and spinal marrow. 

 In its transverse bend, between the atlas and occiput, it 

 distributes a number of branches to the posterior recti and 

 oblique muscles of the head. It supplies also the spinal 

 nerves, and at the foramen magnum gives off the anterior 

 and posterior spinal arteries that descend the cord its whole 

 length. The remaining branches of the vertebral and 

 basilar arteries, are given in the account of the brain. 



The thyroid axis arises from the subclavian at its upper 

 part and near the inner edge of the scalenus anticus. It is 

 a short, thick trunk, and gives off four principal branches : 



The inferior thyroidj the superior scapular or transver- 

 salis humerij the posterior scapular or transversalis collij 

 and the cervicalis anterior or ascending cervical. 



The inferior thyroid ascends behind the common carotid 

 to the thyroid gland, where it anastomoses with the supe- 

 rior thyroid, supplying in its course the trachea, oesopha- 

 gus, and lower part of the larynx. 



The superior scapular proceeds behind the clavicle ob- 

 liquely outward to the supra scapular-notch, over whose 

 ligament it passes to supply the supra-spinatus, and then 

 goes beneath the acromion to the infra-spinatus and teres 



