BLOOD VESSELS OF THE BRAIN 385 



forated spot), they supply the hypothalamus, the thalamus, and the medial 

 part of the pedunculus cerebri. 



The postero -lateral central arteries are small slender twigs which arise 

 on the lateral surface of the pedunculus cerebri, and go to the lamina 

 quadrigemina and the thalamus. 



The posterior chorioidal artery goes to the tela chorioidea of the third 

 ventricle and the chorioid plexus of the lateral ventricle (Figs. 148 and 

 163). 



The cortical branches are distributed to the medial, 

 inferior, and supero-lateral surfaces of the posterior part of 

 the hemisphere (Figs. 146, 147, 148). 



The temporal branches, two or three in number, turn laterally, over the 

 hippocampal gyrus, and ramify on the inferior surface of the temporal lobe 

 of the cerebrum (Figs. 146 and 147). 



The calcarine branch follows the calcarine fissure to the occipital pole 

 of the cerebral hemisphere, round which it turns to reach the lateral surface 

 of the occipital lobe. It is the chief artery of supply to the cuneus and the 

 lingual gyrus, and is therefore specially concerned in the nutrition of the 

 visual centres of the cerebral cortex (Fig. 146). 



The parieto-occipital artery is the smaller of the two terminal branches 

 of the posterior cerebral. It runs upwards in the parieto-occipital fissure, 

 and at the supero-medial margin of the hemisphere it curves laterally to 

 reach the supero-lateral surface of the occipital lobe. It supplies branches 

 to the cuneus and praecuneus (Figs. 146, 148). 



Arteria Carotis Interna. The cut extremity of the internal 

 carotid artery will be found at the lateral side of the optic 

 chiasma, in the angle between the optic nerve and the optic 

 tract. Thence the artery turns laterally, below the substantia 

 perforata anterior, close to the commencement of the lateral 

 fissure, and it ends by dividing into the anterior and middle 

 cerebral arteries (Fig. 144). The middle cerebral artery is the 

 larger of the two terminal branches. It appears to be the 

 continuation of the parent trunk and it runs laterally into the 

 stem of the lateral fissure. The anterior cerebral artery, on 

 the other hand, passes ' medially from the internal carotid, 

 almost at a right angle. Consequently emboli pass more 

 frequently into the middle cerebral than into the anterior 

 cerebral artery. From each internal carotid artery, after it 

 has emerged from the cavernous sinus (p. 239), the following 

 branches arise : 



1. Ophthalmic (already studied, I 3. Chorioidal. 



p. 252). 4. Middle cerebral. 



2. Posterior communicating. 5. Anterior cerebral. 



Arteria Communicant Posterior. The posterior communi- 

 cating artery, as a rule, is a slender branch which passes 

 VOL. in 25 



