362 



INTERNAL CAROTID ARTERY. 



pierce the sclerotic within a line or two of the margin of the cornea. All these 

 ciliary arteries anastomose together within the eyeball, their distribution in which 

 will be particularly described with the anatomy of the eyeball. 



(e) The muscular branches, subject to much variety, usually arranged in an upper 

 and lower set, supply the muscles of the orbit. 



(/) The ethmoidal branches are two in number, a posterior and an anterior. They 

 pass through the posterior and anterior internal orbital foramina, the latter in 

 company with the nasal branch of the ophthalmic nerve ; and both arteries, having 

 furnished branches to the ethmoidal cells, enter the skull, supply the adjacent dura 

 mater, and send branches through the cribriform lamella to the nose. 



(a) The two palpebral branches, superior and inferior, arise near the front of the 

 orbit, usually together, but soon diverge, one lying above, the other below the 

 tendon of the orbicularis muscle at the inner angle of the eye ; they form arches, 

 one in each lid, and send branches to the caruncula lachrymalis and the lachrymal 

 sac. 



(Ji) The nasal branch courses forwards above the tendon of the orbicularis muscle 

 to the root of the nose, where it ramifies, maintaining a free communication with the 

 nasal and the angular branches of the facial artery. 



(i) The frontal branch runs close to the preceding, but on reaching the margin of 

 the orbit turns upwards on the forehead, where it anastomoses with the supraorbital 

 artery. 



Fig. 261. Fig. 201. VIEW OP THE 



DISTRIBUTION OF THE 

 BRANCHES OF THE IN- 

 TERNAL CAROTID AND 

 VERTEBRAL ARTERIES TO 



THE LOWER PARTS OF 



THE BRAIN (altered 

 from Hirschfeld and 

 Leveille). g 



On the left side of the 

 brain a portion of the 

 middle lobe of the cere- 

 brum has been removed so 

 as to open up the fissure of 

 Sylvius and expose the 

 convolutions of the island 

 of Reil ; and the left half 

 of the cerebellum has been 

 removed to show the lower 

 surface of the posterior 

 cerebral lobe. 1, placed 

 on the optic commissure, 

 points to the divided stem 

 of the left internal carotid 

 artery where its cerebral 

 distribution begins ; 2, 

 anterior cerebral branch, 

 exposed fully by the re- 

 moval of a portion of the 

 left optic nerve ; 2', placed 

 on the knee or anterior 

 bend of the corpus callo- 



sum between its two arteries ; x , placed on the lamina cinerea in front of the optic 

 commissure, marks the anterior communicating artery ; 3, middle cerebral artery, 

 passing into the fissure of Sylvius and distributing its branches over the convolutions of 

 the island of Reil and others beyond; 4, placed between the infundibulum and the 

 corpora albicantia, points by a line to the left posterior communicating artery ; 5, basilar 

 artery ; 6, posterior cerebral artery, its distribution exposed on the left side by the 

 removal of half the cerebellum ; 7, placed on the pons Varolii, points to the right 

 superior cerebellar artery ; 8, anterior inferior cerebellar artery ; between 7, and 8, one of 

 the largest of the transverse branches of the basilar artery ; 9, 9, right and left vertebral 

 arteries ; 10, posterior inferior cerebellar arteries ; 11, anterior spinal arteries. 



