580 



THE AETEBIES. 



constitutes the posterior communicating artery ; the other soon bifurcates to 

 form the middle and anterior cerebral arteries. 



Fig. 285. 



ABTBRIES OP THE BEAIK. 

 B, Medulla oblongata ; p, Pons Varolii ; L, Mastoid lobule ; 0, Olfactory lobule ; 

 c, Chiasma of the optic nerves ; M, Mamillary, or pisiform tubercle ; H, Pituitary 

 gland ; three-fourths have been excised. — 1, 1, Cerebro-spinal arteries ; 2, Median 

 spinal artery ; 3, Lozenge-shaped anastomosis of the two cerebro-spinal arteries, 

 from which result, in front : — i, The basilar trunk (usually the cerebro-spinal 

 arteries arrive in the middle of the lozenge) ; 5, 5, Posterior cerebellar arteries ; 

 6, Anterior ditto ; 7, Internal carotid artery, with the two curves it makes in 

 the cavernous sinus ; 8, Internal carotid on the sides of the pituitary gland ; 9, 

 Transverse reticulated anastomosis thrown between the two internal carotids 

 behind the pituitary gland; 10, Bifurcation of the internal carotid; 11, 11, 

 Posterior cerebral arteries anastomosing behind the pisiform tubercle, receiving 

 in the middle of this anastomosis the two terminal branches of the basilar trunk ; 

 12, Middle cerebral artery ; 13, Anterior cerebral artery ; 14, Posterior com- 

 municating artery. 



