THE NERVOUS SYSTEM 



1453 



The transverse or pontine arteries are numerous, and pass out- 

 wards on either side to supply the pons, the sensory and motor roots 

 of the fifth cranial ner\-e, and the middle peduncle of the cere- 

 bellimi. 



The internal auditory artery, long and slender, accompanies the 

 auditory nerve through the internal auditory meatus, and is dis- 

 tributed to the internal ear. 



The anterior inferior cerebellar artery arises from the centre of the 

 basilar, and passes backwards to be distributed to the anterior part 

 of the inferior surface of the cerebellar hemisphere. It anastomoses 

 with the posterior inferior cerebellar arterj% which is a branch of the 

 vertebral. 



The superior cerebellar artery arises from the basilar close to its 



13 15 r4 



Fig. 608. — The Arteries at the Base of the Brain, and the 

 Circle of Willis. 



1. Internal Carotid 



2. Middle Cerebral 



3. Anterior Cerebral 



4. Anterior Communicating 



5. Posterior Communicating 



6. Posterior Cerebral 



7. Basilar 



8. Superior Cerebellar 



9. Transverse Pontine 



10. Internal Auditory- 



11. .A.nterior Inferior Cerebellar 



12. Posterior Inferior Cerebellar 



13. Vertebral 



14. Anterior Spinal 



15. Posterior Spinal 



16. Anterior Choroid 



17. Posterior Choroid 



18. Central or Ganglionic 



19. Central or Ganglionic 



20. Central or Ganglionic 



(Postero-mesial) 



21. Central or Ganglionic 



(Postero- lateral) 



termination. It passes outwards, parallel to the posterior cerebral 

 arterv% from which it is separated by the third cranial nerve. It 

 then winds round the outer side of the cms cerebri, below the fourth 

 cranial ners'e, and so reaches the superior surface of the cerebellar 

 hemisphere, where it divides into branches. These supply the 

 superior vermis, the valve of Vieussens, the velum interpositum, 

 and the superior surface of the cerebellar hemisphere, at the peri- 

 pher\' of which they anastomose with branches of the inferior 

 cerebellar arteries. 



Posterior Cerebral Artery. — ^This is one of the terminal branches 

 of the basilar arter^', at the upper border of the pons Varolii. It 

 passes at first outwards, beneath the crus cerebri, and parallel to 

 the superior cerebellar artery, from which it is separated by the 



