674 THE ARTERIES. 



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 around it by the retractor. 



Entering the cranium, the ophthalmic artery passes inward along a groove 

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

 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 retince 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 

 the 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 palpebrarum, external temporo-auricularis muscle, as well as to 

 the integument of the frontal region (Fig. i581, 85). 



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. 881, 36). 



The cerebral brandies 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 to the 

 dura mater, and particularly to the falx cerebri, anastomoses in the middle line, 

 below the process of the crista galli, with that of the opposite side, and after- 

 wards joins the anterior cerebral artery. 



The nasal branch traverses the cribriform plate of the ethmoid bone, and 

 divides into a number of ramuscules, which descend either on the ethmoidal cells, 

 or on the middle septum of the nose, where their ramifications form arterial tufts 

 of a pleasing aspect. 



8. Buccal Artery (Fig. 881, 87). — The buccal artery emerges at an acute 

 angle from the internal maxillary, a short distance in front of the orbital hiatus, 

 and descends obliquely between the maxillary bone and the superior insertion 

 of the internal pterygoid muscle, terminating in the posterior part of the molar 

 glands, and in the buccinator and depressor labii inferioris muscles. 



In its course it gives some insignificant ramuscules to the pterygoid muscles, 

 as well as to the masseter, and a long branch to the adipose cushion in the temporal 



