LACRYMAL ORGANS. 



93 



perior fork, however, has a few of its fibres 

 blended with the ciliaris." 



The action of the muscle appears to be to 

 direct the lacrymal papilke and points in to- 

 wards the lacus lacrymalis, and to assist in 

 keeping the edges of the eyelids properly ad- 

 justed to the eyeball. 



Nerves. The parts of the organ of vision 

 which have been just described receive their 

 nerves from the fifth and seventh pairs ; the 

 former communicating sensibility, the latter the 

 power to move. See articles, FIFTH PAIR OF 

 NERVES, and SEVENTH PAIR OF NERVES. 



The first division of the fifth pair gives 

 nerves not only to the accessory parts of the 

 eye, but supplies also the eyeball ; hence it is 

 called ophthalmic. The second division of the 

 fifth sends filaments to the lower eyelids. 



Nerves from the first division of the fifth 

 distributed to the accessory parts of the eye. 

 The first division of the fifth pair or the oph- 

 thalmic divides into three nerves, thej'ron 

 tul, the nasal, the lacrymal. 



1. Frontal nerve. The supra-trochlear 

 branch of this nerve gives filaments to the 

 upper eyelid and inner canthus. The continu- 

 ation of the frontal nerve sends filaments to the 

 upper eyelid and external canthus. 



2. Nasal nerve. The infra-trochlear branch 

 of this nerve supplies the parts at the inner 

 canthus, the conjunctiva, the lacrymal caruncle 

 and lacrymal sac ; it also gives filaments to 

 the orbicularis palpebrarum. The tensor tarsi* 

 receives two twigs from it. The infra-trochlear 

 sends branches upwards, which anastomose 

 with those of the supra-trochlear. 



3. Lacrymal nerve. After supplying the 

 lacrymal gland the branches of this nerve 

 emerge from it, and ramify in the conjunctiva, 

 orbicularis muscle, and skin of the eyelids. 

 The lacrymal nerve forms anastomoses with 

 other branches of the fifth. 



Nerves from the second division of the fifth 

 pair distributed to the accessory parts of' the 

 eye. The principal of these is the inferior 

 palpebral branch of the infra-orbital. The in- 

 ferior palpebral nerve divides into two branches, 

 an external and an internal, which indeed 

 may be separate from the first. 



The external branch runs in the substance of 

 the lower eyelid, distributing branches in its 

 course, to the outer canthus, where it anasto- 

 moses with the inferior palpebral filaments of 

 the lacrymal nerve. 



The internal branch supplies the part of the 

 lower eyelid towards the nose, and terminates 

 in the parts at the inner canthus, anastomosing 

 with a branch of the infra-trochlear. 



The facial orpartio dura of the seventh pair. 

 Of the accessory parts of the eye, the orbi- 

 cularis muscle is that which receives branches 

 from the portio dura of the seventh pair ; per- 

 haps, also, the tensor tarsi muscle, as Mac- 



* Rosenmliller, Icones chirurgico-anatomicae. 

 Weimar, 1805. 



Trasmondi, Intorno la Scoperta di due Nervi 

 dell' Occhio umano ragguaglio. Estratto dal Gi- 

 ornale Arcadico, t. xix. p. 1. Roma, 1823. 



kenzie conjectures. These branches of the 

 portio dura freely anastomose with the branches 

 of the fifth pair above described. 



To this superficial notice of the nerves of 

 the accessory parts of the eye described in this 

 article, all that requires to be added is, that the 

 levator palpebrae superioris receives its nervous 

 filaments from the third pair. 



Bloodvessels. 1 . Arteries. The branches of 

 the external carotid ramified on the face and 

 the ophthalmic artery from the internal carotid 

 are the sources from which the accessory parts 

 of the eye receive their arteries. 



The branches of the external carotid in the 

 face, viz. the facial, the infra-orbital of the in- 

 ternal maxillary, the transverse artery of the 

 face and the temporal send ramifications to the 

 eyelids. Towards the inner canthus the facial 

 ends in the angular artery, which anastomoses 

 with the nasal branch of the ophthalmic. The 

 angular artery, or some one of its branches, is 

 implicated in the operation for fistula lacry- 

 malis as it is called. 



The ophthalmic artery gives off the lacrymal, 

 usually one of its first branches after its en- 

 trance into the orbit. The lacrymal supplies 

 the upper and lower masses of the lacrymal 

 gland, besides other parts in the orbit, and at 

 last issues from that cavity at the external 

 angle of the eye. The muscular arteries of the 

 ophthalmic, after supplying the recti muscles, 

 are continued forward on the front of the eye- 

 ball one from the external rectus muscle, and 

 two from each of the other recti. These arte- 

 ries divide into two sets of branches, of which 

 one set ramify in the ocular conjunctiva, and 

 the other set supply the sclerotica. 



The.ophthalmic, as it issues from the orbit at 

 the internal canthus, gives off the palpebral 

 arteries, superior and inferior. These ramify, 

 in their respective eyelids, towards the external 

 angle, where they meet and inosculate with the 

 terminating branches of the lacrymal artery. 

 The superior palpebral artery, moreover, inos- 

 culates with the supra-orbital and anterior tem- 

 poral ; the inferior palpebral artery with the 

 nasal branch of the ophthalmic, the infra- 

 orbital and transverse artery of the face, thus 

 forming the tarsal or palpebral arches. 



The ramifications sent, from the branches of 

 the external carotid in the face, to the eyelids, 

 and those from the ophthalmic, form by their 

 inosculations a network, from which are sup- 

 plied the different structures of the eyelids, the 

 conjunctiva, the lacrymal caruncle, and the 

 lacrymal sac. 



Where the ocular and palpebral portions of 

 the conjunctiva run into each other, bloodves- 

 sels from the muscular enter and subdivide into 

 two sets of branches one set smaller, to the 

 ocular conjunctiva, the other set larger, to the 

 palpebral conjunctiva. The latter receives 

 another and a still larger set, which enter it at 

 the orbital margin of the tarsal cartilages, 

 anastomose with the first set, and ramify for- 

 wards to the free margin of the eyelids. 



The bloodvessels of the ocular conjunctiva 

 are few and small in comparison to those of 

 the palpebral. They affect a reticular arrange- 



