310 SPECIAL ANATOMY. 



The right is covered before by m. sterno-thyreoid.^ ven. anonyma, 

 n. vagus and phrenicus, m. cleido-mastoid, behind, separated by 

 n. recurrens from m. longus colli ; bounded internally, only a 

 little, by v. cephalica, covered externally by the pleura; sur- 

 rounded all round by lymphatic glands, loose uniting tissue, and 

 plexus of n. sympathicus. 



The left passes parallel with v. cephalica, lies immediately upon 

 longus colli ; and is covered to a greater extent by the pleura ; 

 otherwise like the right. 



The second portion lies close above the centre of the first rib in 

 the space between the mm. scaleni ; below the two scaleni ; before 

 the plexus brachialis ; behind scalen. anticus, before which v. 

 subclavia lies. 



The third portion reaches from the outer border of the scalenus 

 antic, to the clavicle, lies in the triangular fossa supraclavicularis ; 

 behind ven. subclavia^ m. subclavius and clavicula ; before plexus 

 brachialis ; under m. platysmam., skin [supra-clavicular, nerves], 

 and the obliquely crossing art. et ven. suprascapularis ; over the 

 first rib. 



554. Superior branches of Art. subclavia. 



1. Art. vertebralis, the vertebral artery, the largest branch of the subclavia, 

 supplies the spinal cord, medulla oblongata, the small and the posterior parts 

 of the great brain. Or: at the superior, posterior wall of the subclavia, at 

 the commencement from the arch. Course: vertically upwards and rather 

 backwards, it enters between proc. transvers. of the sixth cervical vertebra 

 into the canalis vertebralis, and ascends, slightly curved, to the second, turns 

 backwards between this and the atlas, more still between atlas and foramen 

 magnum behind proc. condyloid. occipit., and enters the skull through lig. 

 obturatorium and dura mater, round to the front of medulla oblongata, ascends 

 upon pars basilaris, and unites with the art. basilaris of the other side. Po- 

 sition : at first very deep between m. longus colli and scalenus antic., behind 

 art. thyreoid. inferior, then in canal, vertebralis, in the interspaces covered by 

 mm. intertransversarii and before the nn. cervicales ; the first curvature be- 

 tween m. trachelomastoid. and obliq. infr. ; the second between obliq. sup. 

 rectus capit. minor and lig. obturatorium ; in the cranial cavity : at the sides 

 and before medulla oblongata. 



Branches. In the neck : 



a. Eami spinales pass through the foram. intervertebral. to the spinal cord. 

 Several come from art . cervicalis and pkaryngea ascendentes. 



b. Eami dorsales pass to the deep cervical muscles above the transverse pro- 



