902 THE VASCULAR SYSTEM. 



sinus, in relation with the oculomotor, trochlear, the ophthalmic division of the trigeminal, 

 and the abducens nerves laterally, and with the endothelial wall of the sinus medially. 

 When it reaches the lower root of the small wing of the sphenoid it turns upwards to the 

 medial side of the anterior clinoid process, pierces the inner layer of the dura mater, and 

 comes into close relation with the inferior surface of the optic nerve immediately 

 posterior to the optic foramen. It then turns abruptly backwards below the optic 

 nerve, and on the medial side of the anterior clinoid process which it frequently grooves ; 

 inclining laterally, it runs between the optic and oculo-motor nerves, and below the 

 anterior perforated substance, to the medial end of the stem of the lateral fissure (Sylvius), 

 where it turns upwards, at some distance from the corresponding lateral border of the 

 optic chiasma, and, after piercing the arachnoid, divides into its two terminal branches, 

 the anterior and middle cerebral arteries. 



BRANCHES OF THE INTERNAL CAROTID ARTERY. 



Branches are given off from the internal carotid in the temporal bone and in 

 the cranium, but, as a rule, no regular branches are given off in the neck. 



In the Temporal Bone. (1) A carotico-tympanic branch, very small, perforates the 

 posterior wall of the carotid canal, and anastomoses in the tympanum with the stylo-mastoid 

 artery and with the tympanic branches of the internal maxillary and ascending pharyngeal 

 arteries. 



(2) A small and inconstant branch which accompanies the nerve of the pterygoid 

 canal (Vidian) ; it anastomoses with a branch of the descending palatine artery. 



In the Cranium. (1) Cavernous, small branches to the walls of the cavernous sinus 

 and to the oculomotor, trochlear, trigeminal, and abducens nerves. 



(2) Minute twigs which supply the sernilunar ganglion. 



(3) Hypophyseal branches pass to the hypophysis (O.T. pituitary body). 



(4) Meningeal branches ramify in the dura mater of the middle cranial fossa, anasto- 

 mosing with the branches of the middle and accessory meningeal arteries. 



(5) Arteria Ophthalmica. The ophthalmic artery (Fig. 761) springs from 



Intermediate medial frontal artery Corpus callosum Septum pellucidum 



Posterior medial frontal artery 



Parieto-occipital 

 artery 



Medial orbital 

 artery 



Anterior cerebral 

 artery 



Lateral orbital arterj 



Middle cerebral artery / - jiiBP^^^^X^ Calcarine artery 



Temporal branch of middle cerebral Posterior cer- Pedunculus Temporal branches of posterior cerebral 



ebral artery cerebri 



FIG. 762. DISTRIBUTION OF THE CEREBRAL ARTERIES ON THE MEDIAL AND INFERIOR SURFACES 



OF THE CEREBRAL HEMISPHERES. 



The anterior cerebral artery is coloured green, the middle cerebral artery red, and the 

 posterior cerebral artery orange. 



the antero-medial side of the internal carotid as it turns upwards on the medi* 

 side of the anterior clinoid process. It passes forwards and laterally, below th 

 optic nerve and through the optic foramen into the orbital cavity. In tt 

 orbit it runs forwards, for a short distance, on the lateral side of the optic nerv 

 and it is in relation laterally with the ciliary ganglion and the lateral recti 



