DISSECTION OF THE HEAD AND NECK. 157 



verse muscles. The dorsal portion of the muscle is seen in the 

 dissection of the thorax (Plates 22 and 25), where its fibres take origin 

 from the bodies of the first six dorsal vertebrae, and pass forwards to 

 terminate in a tendon inserted into the 6th cervical vertebra. In the 

 neck the fibres of the muscle take origin from the transverse processes, 

 and each bundle passes with a forward and inward direction, to be 

 inserted into the body of a vertebra anterior to that from which it arises. 

 The most anterior fasciculi terminate in a tendon inserted into the 

 tubercle of the atlas. 



Action. — To bend the neck downwards. 



Directions. — The vertebral vessels and the accompanying nerve should 

 now be exposed by the careful removal of the intertransversales muscles, 

 attention being at the same time directed to the superior and inferior 

 primary branches of the spinal nerves. These nerves emerge in 

 common from the intervertebral foramina, but separately pierce the 

 muscles. 



The Vektebral Artery is a branch of the axillary artery, given off 

 from that vessel before it leaves the thorax. It enters the neck by 

 passing forwards to the inner side of the 1st rib a little below its upper 

 end. It then ascends along the side of the spinal column, passing 

 first beneath the transverse process of the 7th vertebra, and then in 

 succession through the vertebral foramina of the other bones as far as 

 the axis. Between the last-mentioned bone and the atlas it joins 

 directly the retrograde branch of the occipital artery, but this is not to 

 be exposed at present. It throws off in its course (1) muscular and 

 (2) spinal branches. The former are very numerous and consist of an 

 upward, a downward, and an outward set. Many of the upward set 

 cross over the vertebrse, and anastomose with branches from the superior 

 cervical artery. The spinal branches are detached from the inner side 

 of the artery; and entering the spinal canal by the intervertebral 

 foramina, they join the middle spinal artery in supplying the spinal cord 



and its coverings. 



The Vertebral Vein accompanies the artery, and withm the chest 



joins the anterior vena cava. 



The Vertebral Nerve runs in close company with the vessels. It 

 is formed by the union of filaments from the inferior primary branches 

 of the cervical nerves from the 2nd to the 7th. In the thorax it joins 

 the inferior cervical ganglion of the sympathetic nerve. It is thus 

 a composite nerve made up of the afferent filaments sent by the before- 

 mentioned spinal nerves to the sympathetic cord. 



The LiGAMENTUM NucH^ (Fig. 18). This IS the largest ligament in 

 the body It is placed on the middle plane of the neck, above the 

 vertebri' and it consists of a right and a left division, each of which, 

 again comprises a funicular and a lamellar portion. The entire liga- 



