266 THYROID AND VERTEBRAL ARTERIES. 



terminates on the rectus abdominis muscle, in branches which 

 anastomose with those of the epigastric artery. In this course, 

 it gives branches to almost all the parts to which it is contig- 

 u6us, viz. to the muscles and glands at the lower part of the 

 neck; to the thymus gland; to the parts in the intercostal 

 spaces ; to the sternum ; to the mediastinum and pericardium ; 

 to the diaphragm and to the muscles of the abdomen. 



From some of its ramifications upon the parts between the 

 ribs, small branches go off to the rnamma, and thereby give a 

 name to the artery. There is also a small vessel which is sent 

 off by the mammary artery, or by one of its upper branches 

 which accompanies the phrenic nerve to the diaphragm. 



The Inferior Thyroid Artery 



Arises from the upper side of the subclavian nearly opposite 

 to the origin of the internal mammary. It passes upwards and 

 inwards, between the carotid artery and the spine, to the thy- 

 roid gland : and then it anastomoses with the branches of the 

 superior thyroid on the same side, and with those of its fellow 

 on the opposite side. 



This vessel sometimes sends off large branches to the muscles 

 at the lower part of the neck. One called the ascending cervi- 

 cal, usually arises from it and runs upwards between the edges 

 of the scalenus anticus and rectus anticus major, ramifying on 

 these muscles and anastomosing with branches sent from the 

 vertebral artery. 



The Vertebral Artery 



Arises from the upper and posterior part of the subclavian. 

 It goes upwards and backwards between the muscles which 

 lie on the front of the spine, and passing under the transverse 

 process of the sixth or seventh cervical vertebra, enters into 

 the canal formed in the transverse processes of the vertebrae. 

 In this course, as it proceeds from the third to the second cer- 

 vical vertebra, it inclines outwards laterally, and, in its passage 

 from the transverse process of the second to that of the first 

 vertebra, it forms a considerable curve, the convexity of which 



