368 



SUBCLAVIAN ARTERIES. 



it, where it lies on the groove of the atlas, and at that point the artery is 

 covered by the superior oblique muscle. 



Within, the skull it turns round the side of the medulla oblongata, be- 

 tween the origin of the hypoglossal nerve and the anterior root of the 

 suboccipital, and then lies between the anterior surface of the medulla and 

 the basilar process of the occipital bone. 



Fig. 263. 



Fig 263. DEEP DIS- 

 SECTION OF THE SUB- 

 CLAVIAN ARTERY ON THE 

 RIGHT SIDE, SHOWING 

 THE ORIGIN AND COURSE 

 OP THE VERTEBRAL 

 ARTERY (from Tiede- 

 mann). ^ 



a, Upper pai-t of the 

 sterno-mastoid muscle, its 

 clavicular part divided 

 below ; 6, spinous process 

 of the axis ; c, superior 

 oblique muscle ; d, placed 

 on the inferior oblique 

 muscle, points by a line 

 to the posterior arch of the 

 atlas vertebra ; e, semi- 

 Bpinalis colli ; /, placed 

 on the longus colli, points 

 to the transverse process 

 of the sixth cervical ver- 

 tebra ; </, on the first rib, 

 points to the scalenus 

 anticus muscle cut near 

 its attachment ; 1, inno- 

 minate artery ; 2, right 

 common carotid ; 3, right 

 subclavian ; below it, the 

 origiu of the internal 

 mammary artery ; above 

 it, 4, the thyroid axis, 

 its branches cut short ; 

 5, vertebral artery, pass- 

 ing up through the canal 

 of the transverse pro- 

 cesses and giving branches 

 to the muscles ; 5', placed 

 on the rectus major, points 

 to its horizontal part on 



the arch of the atlas ; 6, placed on the lower part of the divided scalenus medius, points 

 to the trunk of the deep ceivical and first intercostal arteries ; 6', placed on the sealenus 

 medius, points to the deep cervical artery ; 7, occipital arteiy emerging from below the 

 sterno-mastoid and other muscles attached to the mastoid process. 



BRANCHES. A. Cervical branches : 



(a) In the neck, the vertebral artery sends off at different points of its course 

 several small branches named spinal arteries. Each of these, entering the spinal 

 canal through an intervertebral foramen, divides into two branches; one of these 

 passes along the roots of the spinal nerves, supplying the spinal cord and its mem- 

 branes, and anastomoses with the other spinal arteries ; the other branch ramifies 

 on the back part of the bodies of the vertebrae,- in the same manner as similar branches 

 derived from the intercostal and lumbar arteries. 



