THE POSTERIOR COMMUNICATING ARTERY. 



751 



mosis with the middle meningeal branch of the internal maxillary through the lachry- 

 mal branch, and communicates also with the spheno-palatine artery by means of the 

 ethmoidal branches. The anastomosis 



of the nasal branch with the angular ar- 

 tery from the facial is also a large one, the 

 two vessels being practically continuous. 



Variations. — In addition to the varia- 

 tions in the number and origins of its 

 branches, the ophthahnic artery also presents 

 variations in its course, in that, instead of pass- 

 ing to the inner wall of the orbit above the op- 

 tic nerve, it sometimes passes below that 

 structure. The most striking variation which 

 it presents, however, is associated with the 

 development of the branch of the lachrymal 

 artery, which passes back through the sphe- 

 noidal fissure to anastomose with the middle 

 meningeal (Fig. 698). Occasionally this 

 branch becomes exceptionally large and forms 

 the main stem of the lachrymal artery, the 

 connection of that vessel with the ophthalmic 

 vanishing, so that it seems to be a branch of 

 the middle meningeal. A further step in this 

 process which sometimes occurs results in the 

 origin of the entire ophthalmic system of ves- 

 sels from the middle meningeal artery. 



Fig 



Supraorbital 



Anterior 

 Ethmoidal 



Posterior 

 Ethmoidal 



Musculo- 



ciliary 

 branches 



Ophthalmic 

 Optic nerve 



Internal 

 carotid 



Lachrymal 



Anastornot- 

 ic branch 



Central 



retinal 



Degenera- 

 ted portion 



From middle 



meningeal 



Variations of ophthalmic artery ; lachn,'mal coming 

 chiefly from middle meningeal. (Meyej.) 



4. The Posterior Communicating Artery. — The posterior communicating 

 artery (a. comraun leans posterior J (Fig. 702) arises from the posterior surface of the 



Fig. 699. 



Branch of ascending frontal artery 

 Parietal artery 



Fissure of Rolando 



Precentral sulcus 



Ascending frontal artery 



Fissure of 

 Sylvius 



Parieto- 

 occipital 

 branch, of 

 posterior 

 cerebral 



Calcarine 

 branches 

 of posteri- 

 or cerebral 



Branches of 

 anterior cere- 

 bral artery from 

 mesial surface 



Great 



^ longitud- 

 inal 

 fissure 



Branches 

 of anterior 

 , cerebral 

 \ artery 



External 

 orbital artery 



Anterior inferior 

 cerebellar artery 



Inferior frontal artery 



Middle cerebral 

 artery 



\ Temporal branches of 

 middle cerebral artery 



^ Parieto-temporal arteries 

 Basilar artery 

 Pons 

 Left vertebral artery 

 Middle cerebellar peduncle 



Right vertebral artery 



Latetal surface of brain, showing cortical branches of middle cerebral artery ; those of anterior and posterior 

 cerebral arteries are seen curving over supero-mesial border of cerebral hemisphere. 



internal carotid, opposite the sella turcica. It is directed backward beneath the 

 optic tract and the inner border of the crus cerebri, and terminates posteriorly by 



