368 DISSECTION OF THE BACK. 



* VESSELS IN THE BACK. The vessels now dissected are the occipital 

 and the deep cervical ; part of the vertebral ; and the posterior branches 

 of the intercostal and the lumbar arteries of the aorta. Veins accompany 

 the arteries for the most part. 



In the neck. The vessels in the neck are the occipital, the vertebral, 

 and the deep cervical. 



The occipital artery (fig. 119, a) courses along the occipital bone. Ap- 

 pearing from beneath the digastric muscle, the vessel is directed back- 

 wards beneath the sterno-mastoideus, the splenius, and sometimes the 

 trachelo-mastoideus, but over the obliquus superior and complexus muscles. 

 Near the middle line it perforates the trapezius, and ascends to the occi- 

 put, on which it is distributed (p. 21). It supplies the surrounding muscles, 

 and furnishes the following branch to the neck : 



The cervical branch (b) (ram. princeps cervicalis) distributes twigs to 

 the under part of the trapezius, and passing beneath the complexus, anas- 

 tomoses with the vertebral and deep cervical arteries. 



The vertebral artery (fig. 119, c) lies on the neural arch of the first 

 vertebra, behind the articulating process, and appears in the interval be- 

 tween the straight and oblique muscles. Beneath it is the suboccipital 

 nerve. Small branches are given to the surrounding parts, and to anasto- 

 mose with the contiguous arteries. 



The deep cervical artery (fig. 119, e) is a branch of the superior inter- 

 costal (p. 78), and resembles the posterior branches of the other inter- 

 costal arteries. Passing back between the transverse process of the last 

 cervical vertebra and the neck of the first rib, it ascends between the coin- 

 plexus and semispinalis muscles, as high as the upper border of the latter, 

 and anastomoses with the cervical branch of the occipital artery. The 

 contiguous muscles receive branches from it, and anastomoses are formed 

 between its offsets and those of the vertebral. 



* In the dorsal region. The posterior branches of the intercostal ves- 

 sels (p. 337) pass back between the vertebrae and the anterior costo-trans- 

 verse ligament, and are divided like the nerves into inner and outer 

 pieces. 



* The inner branches end in the fleshy mass of the multifidus spinoe and 

 semispinalis, and furnish small cutaneous offsets with the nerves. 



* The external branches cross beneath the longissimus dorsi, and supply 

 it and the ilio-costalis. Like the nerves, the lowest branches of this set 

 are the largest and extend to the surface. 



As the dorsal branch of the intercostal artery passes by the interverte- 

 bral foramen, it furnishes a small intraspinal artery to the spinal canal. 



* In the loins. The posterior branches of the lumbar arteries divide, 

 like the intercostal, into internal and external pieces, as soon as they reach 

 the interval between the longissimus dorsi and multifidus spinas. Each 

 gives also a spinal branch to the spinal canal. 



* The internal branches are small, and end in the multifidus spinae 

 muscle. 



* The external branches supply the erector spinaa ; and offsets are con- 

 tinued onwards to the integuments with the superficial nerves. 



VEINS. With the deep cervical artery is a large vein, vena profunda 

 cervicis, which communicates with the occipital and other deep veins in 

 this region, forming the posterior plexus of the neck, and passes forwards 

 with its artery, between the transverse processes, to join the vertebral 

 vein. 



