THE POSTERIOR CEREBEAL ARTERY. 



721 



an. I t-nter the posterior perforated space between the crura cerebri, to 

 supply the optic thalarai in the interior of the brain. They are 

 divide-! into two sets, those near the middle line and those further two sets; 

 out, and are named respectively the postero-mesial and postero -Lateral 

 central arteries. 



2. The posterior choroid artei-y (fig. 258) leaves the parent vessel as 

 it winds round the eras and pursues a parallel course until it turns 

 forwards beneath the posterior end of the corpus callosum to enter 

 the velum interpositum and the choroid plexuses of the ventricles of 

 the cerebrum. 



3. Two or more superficial, or cortical, temporal branches pass 

 outwards from the artery in its course backwards and supply the 

 under surface of the temporal lobe, except at the most anterior and Temporal 

 most posterior parts. 



4. The cakarim: and parieto-occipital, like the foregoing, are cortical Calcariue 

 arteries. The calcarine runs into the posterior limb of the calcarine 



posterior 



choroid 



artery. 



Cortical 

 branches ; 



Ascending parietal. 



Asi-ending frontal. c&r e.bra,l 



External orbital. 



MIDDLE CKREBRAL 



ARTERY. 



Temporal 



Parieto-temporal. 



Fn;. 259. THE OUTER SURFACE OP THE CEREBRAL HEMISPHERE, SHOWING 

 THE DISTRIBUTION OF THE MIDDLE CEREBRAL ARTERY. 



fissure and supplies the back part of the fifth temporal convolution 

 and the adjoining cuneus. The parieto-occipital branch runs mainly Parieto- 

 in the internal parieto-occipital fissure and supplies the front part of occl P ltal - 

 the cuneus and the back part of the pre-cuneate convolution. 



The posterior cerebral artery thus supplies the cortex of the 

 cerebral hemisphere over the whole of the mesial aspect of the 

 temporal (except the most anterior part) and occipital lobes, with a 

 small part of the parietal (pre-cuneus) ; as well as a small part of the 

 corresponding parts on their outer or convex surface (fig. 259). 



From the foregoing examination of the onsets of the vertebral Part of 

 arteries and the basilar trunk, it appears that about half the brain pi^d by P 



viz., the medulla oblongata, the pons, the cerebellum, and the vertebral 



8 A 



