THE ARTERIES 131 



off twigs, which enter the spinal canal through the intervertebral 

 foramina to assist in supplying the structures therein. 



From the extra-thoracic portion of the left axillary artery one 

 branch is given off which concerns us here : 



T/ie Inferior Cervical Artery. — This leaves the axillary artery as 

 the latter turns round the first rib. After a course of from one 

 and a half to two inches it divides into two branches, one 

 of which passes into the groove between the mastoido-humeralis 

 and subscapulo-hyoideus muscles, and the other runs downwards 

 between the mastoido-humeralis and the anterior superficial 

 pectoral, where it is placed alongside the cephalic vein. 



The Innominate Artery. — This vessel gives off a trunk which is 

 common to the superior cervical and dorsal arteries, and the innominate 

 then splits up into the right axillary and cephalic vessels. As already 

 mentioned, the innominate artery is at a lower level than the left axillary. 

 The right axillary artery gives off the vertebral, the course and 

 distribution of which resemble those of the corresponding artery of 

 the left side. 



(i) The Dorso-Cervical Artery takes a short upward course and 

 splits up into the dorsal and superior cervical arteries, which 

 are also distributed as on the left side. Round the dorso- 

 cervical artery, the right recurrent laryngeal nerve curves to 

 take its course up the neck after leaving the vagus. 



(2) The Cephalic Trunk. — This passes forwards on the inferior 

 aspect of the trachea. It is only about two inches long, and 

 it divides into the two common carotid arteries. 



The Common Carotid Artery. — This is the vessel which carries 

 the blood to the head. It is at first placed on the inferior aspect 

 of the trachea, and is related to the scalenus, longus colli, and rectus 



