Fig. 13. Base of Brain with Arteries and Superficial Origin of 



Cranial Nerves. 



The Pia Mater has been removed. Unimportant branches of the Arteries have 

 been cut away; the Pituitary Body has been removed. (Names of Arteries 



cf Fig. 25.) 



The vertical and lateral surfaces of the Cerebrum are of importance in 

 connection with Motor and Sensory Centres while the Base of the Cerebrum 

 demands consideration in connection with the position of the Cranial Nerves and 

 the Arteries. 



Functional disturbance of a single nerve or of a group of nerves will 

 guide us to the seat of a tumour or any other pathological basal lesion which 

 brings about the particular disturbances. It is a remarkable fact that, with the 

 exception of the Olfactory and Optic Tracts which are really outgrowths from 

 the Brain, all Cranial Nerves emerge from the Brain between the upper border 

 of the Pons and the lower end of the Bulb. 



The Superficial (apparent) Origin of the VI th and.XIIth nerves are very 

 close to each other at the posterior border of the Pons and side of the Bulb. 



The course of the nerves after leaving the Brain until they reach their 

 foramina of exit varies in length. The IVth nerve has the longest intra-cranial 

 course, arising on the dorsum of the Mid-Brain (Mesencephalon), near the valve 

 of VlEtfSSENS (cf. Fig. 6), it winds round the Crus to reach the Ventral aspect 

 of the Brain. A portion of the roots of the Spinal Accessory also has a long 

 course arising as it does low in the Cervical portion of the Spinal Cord. 



The brain is supplied with blood from its base through the Internal 

 Carotid and Vertebral Arteries. The two Vertebral Arteries unite to form the 

 Basilar which gives off the Postero-Inferior Cerebellar (this is more often a branch 

 from the Vertebral), the Auditor}^ the Antero-Inferior Cerebellar, and the Superior 

 Cerebellar Arteries. At the inferior border of the Pons the Basilar Artery divides 

 into Right and Left Posterior Cerebral Arteries each of which communicates 

 (posterior communicating) with the Internal Carotid. The Internal Carotid gives 

 off the large Middle Cerebral (Sylvian) Artery, the smaller Choroidal Branches 

 and the Anterior Cerebral Artery. As the two Anterior Cerebral Arteries are 

 connected by the Anterior Communicating in front of the Optic Chiasma a large 

 circular anastomosis is formed round the Sella Turcica (Circle of Willis). 



All the vessels pass to and ramify in the Pia Mater, and give off small 

 branches, which enter the brain and supply it with blood. 



