296 



VERTEBRAL AND BASILAR ARTERIES. 



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 first three being ascend- 

 ing, and the remaining two descending : they are the 



Vertebral, 

 Thyroid axis, 



Profunda cervicis, 

 Superior intercostal, 

 Internal mammary. 



f Inferior x thyroid, 

 I Supra-scapular, 

 1 Posterior scapular, 

 [ Superficial cervicis. 



Fig. 148 * 



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, ex- 

 cepting the last ; then winds backwards 

 around the articulating process of the atlas ; 

 and, piercing the dura mater, enters the skull 

 through the foramen magnum. The two arte- 

 ries unite at the lower border of the pons 

 Varolii, to form the basilar artery. In the 

 foramina of the transverse processes of the 

 vertebraB the artery lies in front of the cer- 

 vical nerves. 



Dr. John Davyf has observed that, when 

 the vertebral arteries differ in size, the left is 

 generally the larger: thus in ninety-eight 

 cases he found the left vertebral the larger 

 twenty- six times, and the right only eight. 

 In the same number of cases he found a 

 small band stretching across the cylinder of 

 the basilar artery, near the junction of the two vertebral arteries, seventeen 

 times, and in a few instances a small communicating trunk between the 

 two vertebral arteries previously to their union. I have several times seen 

 this communicating branch, and have a preparation now before me in 

 which it is exhibited. 



The BASILAR ARTERY, so named from its position at the base of the 

 brain, runs forwards to the anterior border of the pons Varolii, where it 

 divides into four ultimate branches, two to either side. 



Branches. The branches of the vertebral and basilar arteries are the 

 following : 



* 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 portion 

 f>. The third portion. 6. The vertebral artery. 7. The inferior thyroid. 8. The thyroid 

 axis. 9. The suporficialis cervicis. 10. The profunda cervicis. 11. The posterior 

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

 arteiy. 14. The superior intercostal. 



| F'linburgh Medical and Surgical Journal, 1839. 



