588 THE ARTERIES. 



tion, which it turns round to be inflected backwards. This vessel com- 

 municates with the masseteric artery by a fine division, which traverses the 

 sigmoid notch of the maxillary bone. 



6. DEEP ANTERIOR TEMPORAL ARTERY (Fig. 286, 33). Springing at a 

 right angle, like the preceding, in the interior of the subsphenoidal canal, 

 this artery escapes by the superior branch of that conduit, ascends against 

 the bony wall of the temporal fossa, along the anterior border of the temporal 

 muscle, in which it is almost entirely expended. It gives some ramuscules 

 to the adipose tissue of the temporal fossa. Its terminal extremity arrives 

 beneath the internal parieto-auricular muscle, ramifies in it, and in the skin 

 of the forehead. 



7. OPHTHALMIC ARTERY (Fig. 286, 34). This vessel has a somewhat 

 singular arrangement. After being detached from the internal maxillary in 

 the subsphenoidal canal, in front of the deep anterior temporal artery, with 

 which it is sometimes united, it penetrates by the orbital hiatus to 

 the bottom of the ocular sheath ; it then enters the cranium by the orbital 

 foramen, after describing a loop opening backwards and downwards, which 

 passes between the muscles of the eye, beneath the superior rectus, and 

 above the optic nerve and the sheath formed round it by the posterior rectus 

 (or retractor). 



Entering the cranium, the ophthalmic artery passes inwards along a 

 groove in the ethmoidal fossa, and terminates by two branches : a meningeal 

 and nasal. 



Collateral branches. In its orbital track, the ophthalmic artery 

 emits numerous collateral branches, which arise from the convex side of the 

 loop described by this vessel. These are : the muscular arteries of the 

 eye, the ciliary, central artery of the retina, supra-orbital, and lachrymal 

 arteries. 



In its cranial portion, it furnishes the cerebral branches. 



The muscular arteries of the eye have a destination sufficiently indicated 



by their name. Their number and mode of origin vary. They are 



usually two principal, which arise directly from the ophthalmic artery, and 



others of a smaller size furnished by the lachrymal and supra-orbital 



, branches. 



The ciliary arteries, destined to the constituent parts of the globe of the 

 eye, but chiefly to the choroid coat, the ciliary processes, and the iris, 

 are long thin branches, emanating, for the most part, from the muscular 

 -arteries. 



We only mention the centralis retinse artery here ; as it and the ciliary 

 arteries will be described when we come to study the visual apparatus. 



The supra-orbital artery ascends, with the nerve of the same name, against 

 fthe inner wall of the ocular sheath, to gain the supra-orbital foramen ; 

 passing through that orifice, it is distributed to the frontal and supra-orbital 

 muscles, the orbicularis of the eyelids, external temporo-auricularis muscle, 

 ae well as to the integument of the frontal region (Fig. 286, 35). 



The lachrymal artery creeps upwards and forwards, between the muscles 

 of the globe of the eye and the superior wall of the ocular sheath, to terminate 

 in the lachrymal gland and the upper eyelid (Fig. 286, 36.) 



The cerebral branches of the ophthalmic artery vary in number, and 

 frequently there is only one, of somewhat considerable volume. They pass 

 to the anterior extremity of the cerebral lobe, and anastomose with the 

 divisions of the anterior cerebral artery. 



Terminal branches. The meningeal branch, after detaching ramuscules 



