44 DISSECTION OF THE FACE. 



of each lid is sharp at the {interior edge where it touches its fellow ; but is 

 sloped at the posterior, so as to leave an interval between it and the eye- 

 ball for the passage inwards of fluid. 



The eyelashes (cilia) are two or more rows of curved hairs, which are 

 fixed into the anterior edge of the free border of the lid ; they are largest 

 in the upper lid, and diminish in length from the centre towards the sides. 

 The cilia are convex towards one another, and cross when the lids arc 

 shut. 



The STRUCTURE OF THE EYELIDS. Each lid consists fundamentally 

 of a piece of cartilage attached to the bone by ligaments. Superficial to 

 this framework are the integuments with a layer of fibres of the orbicularis 

 palpebrarum, and beneath it the mucous lining of the conjunctiva. The 

 upper lid includes also the tendon of the levator palpebra3. Vessels and 

 nerves are contained in the lids. 



Dissection. The student may learn the structure of the lids on the left 

 side, on which the muscles are dissected. The bit of tow or wool may 

 remain beneath the lids; and the palpebral part of the orbicularis muscle 

 is to be thrown inwards by an incision around the margin of the orbit. 

 In raising the muscle care must be taken of the thin membranous palpe- 

 bral ligament beneath, and of the vessels and nerves of the lid. 



Orbicularis palpebrarum. The palpebral fibres of this muscle form a 

 pale layer which reaches the free edge of the eyelids (p. 36). A thin 

 stratum of areolar tissue without fat unites the muscle with the skin. 



The palpebral ligament is a stratum of fibrous membrane, which is 

 continued from the margin of the orbit to join the lower or free edge of 

 each tarsal cartilage. At the inner part of the orbit the ligament is thin 

 and loose, but at the outer part it is somewhat thicker and stronger. 



The tarsal cartilages, one for each eyelid, are elongated transversely, 

 and give strength to the lids. Each is fixed internally by the ligament of 

 the eyelids, and externally by a fibrous band external tarsal ligament, 

 to the outer part of the orbit. The margin corresponding with the edge 

 of the lid- is free, and thicker than the rest of the cartilage. On the 

 inner surface each cartilage is lined by the mucous membrane or conjunc- 

 tiva. 



The cartilages are not alike in the two lids. In the upper eyelid, where 

 the cartilage is largest, it is crescentic in shape, and is about half an inch 

 wide in the centre; and to its fore part the tendon of the levator palpebra 

 is attached. In the lower lid the cartilage is a narrow band, about two 

 lines broad, with borders nearly straight. 



Ligament of the eyelids (tendo palpebrarum, internal tarsal ligament) 

 is a small fibrous band at the inner part of the oubit, which serves to fix 

 the lids, and is attached to the anterior margin of the lachrymal groove 

 in the upper jaw. It is about a quarter of an inch long, and divides into 

 two processes, which are united with the tarsal cartilages, one to each. 

 This ligament crosses the lachrymal sac, to which it gives a fibrous expan- 

 sion ; and the fleshy fibres of the orbicularis palpebrarum arise from it. 



The Meibomian glands or follicles are placed in grooves on the ocular 

 surface of the tarsal cartilages. They extend, parallel to one another, from 

 the thick towards the opposite margin of the cartilage ; and their number 

 is about thirty in the upper, and twenty in the lower lid. The apertures 

 of the glands open in a line on the free border of the lid near the pos- 

 terior edge. 



Each gland is a small yellowish tube, closed at one end, and having 



