THE BRAIN. 163 



cerebrals external to where the posterior communicating 

 enter, supply the posterior part of the optic thalamus, 

 crura cerebri, and the corpora quadrigemina. (6) The 

 posteromedian group. Arise from the posterior communi- 

 cating and posterior cerebrals, enter the brain (producing the 

 posterior perforated space), and supply the optic thalami. 

 Other branches not supplying the basal ganglia : 

 (i) The anterior choroid, a small branch from the back 

 part of the internal carotid or the middle cerebral, runs back- 

 ward, enters the lower part of the middle horn of the lateral 

 ventricle through the transverse fissure, and supplies the 

 choroid plexuses of the lateral ventricle, hippocampus major, 

 and corpus fimbriatum. (2) The posterior choroid, from 

 the posterior cerebral, supplies the upper part of the 

 choroid plexuses of the lateral ventricles. 



The Cortical System. 



(1) The anterior cerebral takes a course forward and in- 

 ward from the internal carotid, enters the great longitudinal 

 fissure, through which it passes backward, lying close to the 

 corpus callosum, as far as the parieto-occipital fissure. The 

 anterior cerebral gives off three sets of cortical branches, 

 which supply the under, inner, and outer surface (first and 

 part of the second frontal convolutions) of the frontal lobe 

 and the quadrate convolution of the parietal lobe. 



(2) The middle cerebral. This is the larger artery, into 

 which the internal carotid bifurcates at the inner end of the 

 fissure of Sylvius. The artery passes outward, backward, 

 and upward through the Sylvian fissure, until opposite the 

 lower end of the fissure of Rolando, where it divides into 

 four branches, which supply the greater part of the outer 

 surface of the cerebrum. 



The ganglionic branches of the middle cerebral are of the 



