426 



BLOOD-VESSELS OF THE BRAIN. 



ing upon the upper surface of the hemispheres to anasto- 

 mose with the anterior and posterior cerehral arteries. The 

 posterior branch passes hackward to join the posterior cere- 

 bral artery, forming the side of the circle of Willis, and is 

 called the posterior communicating artery. 



FIG. 119. The internal carotid 



sometimes sends off a 

 hranch called the ar- 

 teria 'choroidea, which 

 passes into the mid- 

 dle cornu of the lat- 

 eral ventricle, and is 

 distributed upon the 

 plexus choroides. 



The vertebral arte- 

 ries arise from the sub- 

 clavian, sometimes 

 from the aorta. They 

 ascend in a straight 

 line through the series 

 of foramina in the 

 transverse processes of 

 the six upper cervical 

 vertebrae, anterior to 

 the cervical nerves. At 

 the second vertebra these arteries take a direction outward, 

 and then again ascend vertically through the foramen in 

 the transverse process of the atlas. After this they take a 

 horizontal direction backward, round the superior oblique 

 process of the atlas in a depression at its back part, and 

 then ascend upward and inward through the foramen 

 magnum, into the cranium, penetrating the dura mater a 



FIG. 119 represents the Circle of Willis, surrounding the Sella Turcica. 

 1 Vertebral arteries. 2 The two anterior spinal branches, forming a single 

 trunk. 3 Posterior spinal artery. 4 Posterior meningeal. 5 Inferior cere- 

 bellar. 6 Basilar artery. 7 Superior cerebellar artery. 8 Posterior cere- 

 bral. 9 Posterior communicating branch of internal carotid. 10 Internal 

 carotid. 11 Ophthalmic artery. 12 Middle and cerebral artery. 13 Anterior 

 cerebral arteries. 14 Anterior communicating artery. 



