THE LACHRYMAL APPARATUS. 



7 



facial vein and its tributaries towards the submaxillary lymphatic glands, laterally 

 into the pre-auricular and parotid lymphatic glands. 



Nerves. The levator palpebrse is supplied by the upper branch of the third 

 nerve, the orbicularis palpebrarum by the upper branches of the facial nerve ; the 

 plain muscular tissue of the lids, like that of the orbit generally, by branches of the 

 sympathetic. 



The sensory nerves come from branches of the fifth. The upper lid is mainly 

 supplied by the frontal and supra-orbital, the lower lid mainly by the infra-orbital 

 branches, but at the inner or nasal part the supra- and infra-trochlear branches of 

 the ophthalmic division come to the surface, and assist in supplying the lids and 

 the adjacent lachrymal apparatus, whilst laterally the lachrymal branch of the 



Fig. 7. NERVES OF THK EYELIDS. LEFT EYE. (From Merkel.) 



ophthalmic sends ramifications to the skin over the external angular process, some 

 of which may pass into the upper eyelid (fig. 7). 



The principal nerves run in front of the tarsi between these and the fibres of the 

 orbicularis (fig. 6). From here their branches pass forwards to the skin and back- 

 wards, piercing the tarsi, to the Meibomian glands and conjunctiva. Near the edge 

 of each eyelid, between the tarsus, the orbicularis, and the muscle of Kiolau, is an 

 anastomotic chain of nerve-fibres, the marginal plexus of Mises, from which nerves 

 are supplied to the surrounding parts and to the hair-follicles of the eyelashes. 



THE LACHRYMAL APPARATUS. 



The parts which constitute the lachrymal apparatus are the following, viz. : 

 The gland by which the tears are secreted ; the two canals which collect the fluid 

 near the inner canthus, and the sac with the nasal duct continued from it, through 

 which the tears pass into the inferior meatus of the nose. 



The lachrymal gland (fig. 3, 1), an oblong flattened body, about the size of 

 a small almond, is placed in the upper and outer part of the orbit, a little behind the 

 anterior margin. The upper convex surface of the gland is lodged in a slight 

 depression in the orbital plate of the frontal bone, to the periosteum of which it is 

 united by fibrous bands; the lower surface is adapted to the convexity of the 

 eyeball, and is in contact with the upper and the outer recti muscles. The fore 

 part of the gland, separated from the rest by a thin layer of fascia, and sometimes 

 described as a distinct gland (glandula lacrimalis inferior of Rosenmliller), is 



