

VERTEBRAL ARTERY. 



283 



Plan of the relations of the third portion of the Subclavian Artery. 



Above. 



Supra-scapular artery, 

 Phitysma myoides. 



In Front. 

 Subclavian vein, 

 Subclavius. 



Subclavian Artery, 

 Third portion. 



Behind. 



Brachial plexus, 

 Scalenus posticus. 



Below. 

 First rib. 



Thyroid axis, 





Branches. The greater part of the branches of the subclavian 

 are given off from the artery before it arrives at the margin of the 

 first rib. The profunda cervicis and superior intercostal frequently 

 encroach upon the second portion, and not unfrequently a branch or 

 branches may be found proceeding from the third portion. 



The primary branches are five in number, the three first being 

 ascending, and the latter descending ; they are the - 

 Vertebral, 



Inferior thyroid, 

 Supra-scapular,* 

 Posterior scapular, 

 Superficialis cervicis. 

 Profunda cervicis, 

 Superior intercostal, 

 Internal mammary. 



The VERTEBRAL ARTERY is the first and the largest of the branches 

 of the subclavian artery; it ascends 

 through the foramina in the transverse 

 processes of all the cervical vertebrae, 

 excepting the last ; then winds , back- 

 wards around the articulating process 

 of the atlas ; and piercing the dura 

 mater enters the skull through the 

 foramen magnum. The two arteries 

 unite at the lower border of the pons 

 Varolii, to form the basilar artery. In 

 the foramina of the transverse processes 

 of the vertebrae the artery lies in front 

 of the cervical nerves. 



Dr. John DavyJ has observed that, 

 when the vertebral arteries differ in 

 size, the left is generally the larger : 

 thus in ninety-eight cases he found the 



* This is usually described as arising- from the axillary, but I have most frequently 

 found it to arise from the subclavian. G. 



t The branches of the right subclavian artery. 1. The .arteria innominata. 2. 

 The right carotid. 3. The first portion of the subclavian artery. 4. The second por- 

 tion. 5. The third portion. 6. The vertebral artery. 7. The inferior thyroid. 8. 

 The thyroid axis. 9. The superficialis cervicis. 10. The profunda cervicis. 11. The 

 posterior scapular or transversalis colli. 12. The supra-scapular. 13. The internal 

 mammary artery. 14. The superior intercostal. 



t Edinburgh Medical and Surgical Journal, 1839. 



