444 



TIIK IJRAIN 



It passes downwards on the spinal medulla along the line of 

 the posterior nerve-roots (p. 193). 



Arteria Cerebelli Inferior Posterior. The posterior inferior 

 cerebellar artery is the largest branch of the vertebral artery. 

 It takes origin immediately above the posterior spinal artery, 



Infundibulum 



Abducent nerve 



Trigeminal nerve 

 Trochlear nerve 



Glosso-pharyn- 

 geal nerve 



Accessory nerve 



Section through 



the medulla 



oblongata 



Transverse 



Optic nerve 



Internal carotid 

 artery 



Posterior 

 communicating 

 artery 



--Oculo-motor nerve 

 Posterior cerebra 

 "artery 

 __ Superior 



cerebellar arter 

 Tentorium 



Basilar 

 artery 



Vertebral 

 artery 



Superior petros 

 sinus 



Transverse sinus 



Superior sagittal sinus 



Occipital sinus 



Straight sinus divided 



FlG. 177. Floor of the cranium after the removal of the brain and the 

 Tentorium Cerebelli. The blood vessels forming the Circulus Arteriosus 

 have been left in place. 



and pursues a tortuous course posteriorly, on the side of the 

 upper part of the medulla oblongata, among the fila of the 

 hypoglossal nerve, and then among the fila of the vagus. 

 Finally, turning round the restiform body, it gains the vallecula 

 of the cerebellum, where it ends by dividing into two terminal 

 branches. Of these, one turns posteriorly, in the vallecula, 

 between the inferior vermis and the lateral hemisphere of 

 the cerebellum, whilst the other ramifies on the posterior 



