232 Branches of Subclavian Artery 



the skull through the foramen magnum, joining with its fellow to form 

 the basilar. 



Relations of the root of the vertebral artery. As the vessel 

 comes off at the very beginning of the subclavian, it can be but a little 

 distance upon the outer side of the common carotid : as the internal 

 jugular vein descends upon the outer side of the carotid, and in 

 front of the subclavian artery, it lies just in front of the vertebral 

 artery. 



The sealenus anticus slopes upwards and inwards from the front 

 of the second part of the subclavian to the anterior tubercle of the 

 transverse process of the sixth cervical vertebra, and the longus colli 

 is resting upon the front of the vertebrae : therefore the vertebral artery 

 ascends in the interval between those muscles. 



The thoracic duct, turning downwards and forwards to the con- 

 fluence of the left internal jugular and subclavian veins, passes in front 

 of the root of the vertebral, and the inferior thyroid also winds to the 

 front. The vertebral vein, descending behind the end of the internal 

 jugular, to open into the beginning of the innominate vein, is also to 

 the front of the root of the vertebral artery. 



As the artery courses with the vertebral vein through the trans- 

 verse processes it passes across the emerging cervical nerves, the re- 

 lative position of the structures being similar to the arrangement upon 

 the first rib, that is, the vein is anterior and the nerves are posterior 

 to the artery. 



Ziig-atlon of the vertebral artery. As the artery is ascending 

 on the inner border of the narrow sealenus anticus, and as the outer 

 border of that muscle corresponds to the outer border of the sterno- 

 mastoid, a vertical incision of 2^ or 3 in. down that border of the 

 sterno-mastoid must be only a little to the outer side of the vertebral 

 artery. From the lower end of this incision a second is to be made 

 inwards for about in. through the clavicular origin of the muscle. 

 Then, after the dexterous use of the end of the director, the artery is 

 exposed. The structures in danger are the phrenic and pneumogastric 

 nerves, the internal jugular vein, and the pleura and lung. 



Branches of the vertebral artery (spinal] enter with the roots of the 

 spinal nerves to the cord and its membranes ; others pass out to the 

 muscles and anastomose with the occipital, and with the deep and the 

 ascending cervical arteries. Posterior meningeal branches ramify in 

 the cerebellar dura mater, and posterior and anterior spinal descend 

 along the medulla. The inferior (posterior) cerebellar is a good-sized 

 artery. (The branches of the basilar are referred to on p. 43.) 



The vertebral vein begins outside the back of the skull and passes 

 down through the cervical transverse processes, in front of the vertebral 

 artery. Having traversed the sixth process, it descends on a plane 

 anterior to the first part of the subclavian artery, to end in the back of 

 the innominate vein. It may receive a tributary through the posterior 



