284 BASILAR ARTERY BRANCHES. 



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 pre- 

 viously to their union. I have several times seen this communicating 

 branch, and have a preparation now before me in. which it is ex- 

 hibited. 



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 : 



Vertebral, 



Lateral spinal, 

 Posterior meningeal, 

 Anterior spinal, 

 Posterior spinal, 

 Inferior cerebellar. 



Transverse, 

 Basilar, I Superior cerebellar, 

 ( Posterior cerebral. 



The Lateral spinal branches enter the intervertebral foramina, 

 and are distributed to the spinal cord and 'to its membranes. Where 

 the vertebral artery curves around the articular process of the atlas, 

 it gives oft' several muscular branches. 



The Posterior meningeal are one or two small branches, which 

 enter the cranium through the foramen magnum, to be distributed 

 to the dura mater of the cerebellar fossae, and to the falx cerebelli. 

 One branch, described by Soemmering, passes into the cranium 

 along the first cervical nerve. 



The Anterior spinal is a small branch which unites with its fellow 

 of the opposite side, on the front of the medulla oblongata. The 

 artery formed by the union of these two vessels descends along the 

 anterior aspect of the spinal cord, to which it distributes branches. 



The Posterior spinal winds around the medulla oblongata to the 

 posterior aspect of the cord, and descends on either side, communi- 

 cating very freely with the spinal branches of the intercostal and 

 lumber arteries. Near its commencement it sends a branch upwards 

 to the fourth ventricle. 



The Inferior cerebellar arteries wind around the upper part of the 

 medulla oblongata to the under surface of the cerebellum, to which 

 they are distributed. They pass between the filaments of origin of 

 the hypoglossal nerve in their course, and anastomose with the 

 superior cerebellar arteries. 



The Transverse branches of the basilar artery supply the pons 

 Varolii, and adjacent parts of the brain. One of these branches. 



