1 6 THE MENINGES OF THE BRAIN. 



these great vessels pierce the hemispheres perpendicularly to the 

 surface. They are distributed, the short, to the cortex, and the 

 long, to the medulla of the hemispheres. To a limited extent 

 they anastomose with one another, but they do not communicate 

 with the ganglionic system. 



The anterior cerebral artery (a. cerebri anterior, Figs. 9 and 

 12), a branch of the internal carotid, runs forward and toward 

 the median line above the optic nerve and enters the longitudinal 

 fissure; it is here joined to its mate by a very short artery, the 

 anterior communicating. Winding around the genu of the corpus 

 callosum, it runs back on the medial surface of the hemisphere to 

 the occipito-parietal sulcus. It gives origin to the antero-median 

 ganglionic arteries, and to four groups pf cortical branches: 



(1) The internal orbital artery (Figs. 9 and 10) which supplies 

 the medial orbital gyrus, the gyrus rectus, the optic chiasma and 

 the olfactory bulb, tract, medial and intermediate striae, triangle, 

 and parolfactory area. (2) The anterior internal frontal (Fig. 12) 

 which enters the anterior parts of the gyrus cinguli and superior 

 frontal gyrus on the medial surface and of the superior and middle 

 frontal gyri on the convex surface. (3) The middle internal frontal 

 branches, which are distributed to the middle part of the gyrus 

 cinguli, to the paracentral lobule and to the upper portions of the 

 superior frontal and the anterior and posterior central gyri. (4) 

 The posterior internal frontal branches, which run back to the 

 occipito-parietal sulcus. They supply nearly the whole corpus 

 callosum, the posterior half of the gyrus cinguli, a part of the 

 paracentral lobule, the praecuneus, and the superior parietal 

 lobule. 



The middle cerebral artery (a. cerebri media, Figs. 10 and n) 

 crosses the anterior perforated spot and runs in the lateral fissure 

 of the cerebrum to the posterior sulcus circularis (Reili) where 

 it breaks up into several parieto-temporal branches. It gives 

 origin to the antero-lateral ganglionic arteries, and to four cortical 

 branches: (i) The lateral orbital branches are distributed to 

 the anterior and posterior orbital and the inferior frontal gyri. 



(2) The ascending frontal, two branches, which follow the pre- 

 central and central sulci, supply the anterior central gyrus and 



