236 PRACTICAL ANATOMY. 



THE SUBCLAVIAN ARTERY. 



The subclavian artery curves up into the root of the 

 neck, and at the lower border of the first rib becomes the 

 axillary. As the scalenus anticus muscle passes over 

 the subclavian to be inserted on the tubercle on the first 

 rib. it divides the innominate into three parts, the first 

 part being internal to the inner border of the scalenus 

 anticus, the second part behind the scalenus anticus, the 

 third external to the scalenus anticus. The branches of 

 the subclavian are four in number, two ascending and 

 two descending ; the ascending are the vertebral and 

 thyroid axis from the first part of the subclavian ; the 

 descending are the internal mammary and superior inter- 

 costal ; of these the internal mammary comes from the 

 second part of the subclavian ; there are no branches 

 from the third part. 



THE VERTEBRAL ARTERY. 



The vertebral artery passes up along the side of the 

 cervical vertebrae through the foramina in the transverse 

 processes, and passes behind the articular surface on the 

 atlas, enters the skull through the foramen magnum, joins 

 its fellow and forms the basilar artery, which passes for- 

 ward beneath the pons Varolii, and divides into the pos- 

 terior cerebral arteries. The vertebral sends off branches 

 as follows: 



In the Neck. 



Lateral Spinal. Seven or eight branches which pass 

 through the intervertebral foramina and divide into 

 anterior and posterior branches. 



Muscular. Distributed to the deep muscles of neck. 



In the Cranium. 



Anterior Spinal. From the upper part of the ver- 

 tebral. It anastomoses with its fellow and forms the 



