THE VERTEBRAL AND BASILAR ARTERIES. 719 



round the medulla oblongata, between the pneumo-gastric and spinal 

 ory nerves, to the median groove of the cerebellum. Directed 

 onwards in the sulcus between the hemisphere and the inferior 

 vermiform process, the artery readies the hinder margin of the 

 cerebellum, and there anastomoses with the superior cerebellar 

 artery. 



An offset of this branch ramifies over the under part of the offsets, 

 cerebellar hemisphere, and ends externally by anastomosing with the 

 artery of the upper surface. As the vessel passes by the side of 



- /-- 10 



III 



13 



FIG. 257- DIAGRAMMATIC REPRESENTATION OF THE ARTERIES AT THE 

 BASE OK THE BRAIN. 



1. Internal carotid trunk. 8. Superior cerebellar. 



2. Anterior cerebral. 9. Auditory. 



3. Anterior communicating. 10. Posterior inferior cerebellar. 



4. Middle cerebral. 11. Basilar. 



5. Anterior choroid. 12. Vertebral. 



6. Posterior communicating. 13. Anterior, spinal. 



7. Posterior cerebral. 



The anterior inferior cerebellar artery which passes outwards from the 

 basilar behind Xo. 8 is not indicated by a pointer. 



the fourth ventricle, it gives a small choroid branch to the plexus of 

 that cavity. 



The BASILAR ARTERY ( u ), formed by the union of the two verte- 

 brals, reaches from the lower to the upper border of the pons, where ar 

 it ends by dividing into two branches (posterior cerebral) for the 

 cerebrum. The vessel lies in the median groove of the pons, resting situation ; 

 against the body of the sphenoid bone. On each side of, and almost 

 parallel to it, is the sixth nerve. 



BRANCHES. Besides the two posterior cerebral branches, the artery branches ; 

 supplies transverse offsets to the pons and the fore part of the cere- 

 bellum, and a large branch to the upper surface of the cerebellum. 



