ANGIOLOGY 221 



The posterior vertebral artery passes in the canals of the trans- 

 verse processes of the fifth or sixth dorsal vertebra. It sends 

 branches into the vertebrae, into the spinal canal, and into the 

 intercostal muscles between the ribs and anastomoses with the 

 intercostal arteries. 



The anterior vertebral artery is larger than the posterior. It 

 extends laterally along the side of the neck in the foramen of the 

 transverse processes of the cervical vertebrae, and Hes along the 

 course of the inferior vertebral vein and the deep imbedded trunk 

 of the s3Tnpathetic nerve. It continues to the head. In its passage 

 it gives off to each vertebral segment a dorsal and a ventral branch. 

 Twigs from these branches pass into the bodies of the vertebrae and 

 the spinal canal, giving nutriment to the bony structure and to the 

 spinal cord and its coverings. Other twigs are distributed to the 

 muscles of the neck and some finally anastomose with branches of 

 the carotis communis. This artery, reaching the head, gives off a 

 long anastomosing branch which passes between the atlas and 

 posterior part of the occipital bone and joins the ramus profimdus 

 and the occipital artery, thus again communicating with the carotid 

 artery. The remainder of the vertebral artery is small and passes 

 through the foramen magnum into the cranial cavity where it 

 anastomoses with terminal branches of the cerebral artery. At the 

 base of the neck and before the vertebral artery enters the canal of 

 the cervical vertebrae, it gives off the arteria cervicalis ascendens, 

 superior artery of the crop (Fig. 73, No. 18) which branches out on 

 the upper surface of the crop is also distributed to the neck muscles, 

 and later subdivides into the transverse cervical arteries which 

 supply the skin and the muscles of the base of the neck, and the 

 shoulder region. 



On the ventral side of the neck there are given off two subvertebral 

 carotid arterial branches. They he in a shallow furrow on the 

 ventral side of the cervical vertebrae and close to the median line. 



Branches of the Subclavian Artery 



The subclavian artery (Fig. 20, No. 13; Fig. 73, No. 11) gives off 

 the following branches: 



I. Stemo-clavicularis (Fig. 73, No. 9) which originates on the 

 upper part of the subclavia, between the carotid artery and external 

 thoracic (Fig. 73, No. 3), divides into many branches. The sterno- 



