824 



THE OKGANS OF SENSE. 



from the supra-orbital and frontal arteries. The veins are arranged in two sets : (a) subcon- 

 junctival or retrotarsal, opening into the muscular tributaries of the ophthalmic veins, and (6) 

 pretarsal, into the angular and superficial temporal veins. The lymph vessels, like the veins, 

 form pre- and retrotarsal networks, which communicate with each other through the tarsal 

 plates. The lymph is drained chiefly into the anterior auricular and parotid lymph glands, but 

 partly, by vessels which accompany the anterior facial vein, into the submaxillary lymph glands. 

 The sensory nerves of the eyelids are supplied by the trigeminal nerve the upper lid chiefly 

 by the supra-orbital and supra-trochlear branches of the ophthalmic ; the lower, by the infra- 

 orbital branch of the maxillary. The region of the lateral commissure receives some filaments 

 from the lacrimal nerve, that of the medial from the infra-trochlear. These sensory nerves 

 form a marginal plexus behind the orbicularis oculi muscle. The levator palpebrae superioris 

 muscle is supplied by the oculomotor nerve and the non-striped fibres of the eyelids by the 

 sympathetic. 



APPAEATUS LACEIMALIS. 



The lacrimal apparatus consists of : (1) the lacrimal gland, which secretes the 

 tears ; (2) the lacrimal ducts, by which the tears are drained from the front of the 

 eye ; and (3) the lacrimal sac and naso-lacrimal duct, which convey them into the 

 nasal cavity. 



Lucriinal gland 

 (superior part) 



Temporal muscle - 



Temporal fascia 



Excretory ducts 

 of lacrimal gland 



Lacrimal gland, 

 (inferior part) 



Infra-orbital 

 nerve 



Maxillary sinus - 



Buccinator 



Superior fornix 

 of conjunctiva 



Puncta 

 lacrimalia 

 Lacrimal ducts 

 Lacrimal sac 



Medial palpebral 

 ligament 



Naso-lacrimal 

 duct 



Middle concha 

 Muco- 

 periosteum 

 Plica lacrimalis 

 Inferior meatus 

 Inferior concha 



FIG. 700. DISSECTION TO SHOW THE LACRIMAL APPARATUS. 



Glandula Lacrimalis. The lacrimal gland is a flattened, oval body situated 

 in the superior and lateral part of the orbital cavity ; it consists of two portions 

 superior and inferior imperfectly separated from each other by the expansion of 

 the tendon of the levator palpebrse superioris muscle. The glandula lacrimalis 

 superior is firm and much larger than the inferior ; it measures transversely about 

 20 mm., and sagittally from 12 to 14 mm. It occupies the fossa lacrimalis on the 

 medial surface of the zygomatic process of the frontal bone, and is fixed by fibrous 

 bands to its periosteum, while its inferior surface is in contact with the levator 

 palpebrae superioris and rectus lateralis muscles, which intervene between it and 

 the bulb of the eye. The glandula lacrimalis inferior consists of small, loosely 

 aggregated lobules ; it lies below and in front of the orbital portion, and projects 

 into the posterior part of the upper eyelid, where its deep surface is in contact 

 with the conjunctiva. The ducts draining the glandula superior are from three 

 to five in number ; they pass between the lobules of the glandula inferior, and 

 open at the upper and lateral part of the fornix conjunctivas superior. The ducts 

 of the glandula inferior number from three to nine ; some of them join those 

 from the glandula superior, while others open separately at the fornix conjunctive 

 superior. The lacrimal gland has a structure resembling that of the parotid, and 



