THE APPENDAGES OF THE EYE 



1115 



their margins, the angles of which correspond to the junction of the upper and lower 

 lids, and are called canthi. 



The outer canthus (commissura palpebrarum lateralis) is more acute than the 

 inner, and the lids here lie in close contact with the globe; but the inner canthus 

 (commissura palpebrarum medialis) is prolonged for a short distance inward 



toward the nose, and the two lids are separated at the inner canthus by a. triangular 

 space, the lacus lacrimalis. At the commencement of the lacus lacrimalis, on the 

 margin of each eyelid, is a small conical elevation, the lacrimal papilla, the apex of 

 which is pierced by a small orifice, the punctum lacrimale (Fig. 828), the commence- 

 ment of the lacrimal canal (Fig. 826). When the lids are closed a space remains 

 between them and the globe to permit of the flow of tears inward (rivus lacri- 

 malis). 



The Eyelashes (cilia') (Fig. 824) are attached to the free edges of the eyelids; 

 they are short, thick, curved hairs, arranged in a double or triple row at the margin 

 of the lids; those of the upper lid, more numerous and longer than the lower, 

 curve upward; those of the lower lid curve downward. Because of this arrange- 

 ment the two sets do not interlace in closing the lids. Near the attachment of 

 the eyelashes are the openings of sebaceous glands (glandulae sebaceae} (Fig. 824) 

 and of a number of glands, glands of Moll (glandulae ciliares [MolliJ) (Fig. 824), 

 arranged in several rows close to the free margin of the lid. They are regarded 

 as enlarged and modified sweat glands. 



LACRIMAL ARTERY 

 AND NERVE 



EXTERNAL TARSAL 

 LIGAMENT 



-SUPRAORBITAL VES- 

 SELS AND NERVE 



LACHIMAL SAC 



INTERNAL TARSAL 

 LIGAMENT 



\ 



FIG. 823. The tarsi and their ligaments. Right eye, front view. (Testut.) 



Structure of the Eyelids (Fig. 784). The eyelids are composed of the following structures, 

 taken in their order from without inward: Integument, areolar tissue, fibres of the Orbicularis 

 muscle, tarsal plate, and its Ijyament. Meibomian flands. and conjunctiva. The upper lid has, 

 in addition, the aponeurosis of the Levator palpebrae, while both lids contain a certain amount 

 of nonstriated muscle, called, respectively, the Superior and Inferior tarsal muscles (see p. 369) 

 (Fig. 794). The integument is extremely thin, and continuous at the margin of the lids with 

 the conjunctiva. The subcutaneous areolar tissue is very lax and delicate, seldom contains any 

 fat, and is extremely liable to serous infiltration. The Palpebral fibres of the Orbicularis 

 muscle (?. ciliaris [Riolani]) are thin, pale in color, and possess an involuntary action. 



The tarsal plates (Fig. 823) are two thin elono-ated wedp-e-shaped plates of dense connective 

 tissue about 2.5 cm. (an inch) in length. They are placed one in each lid, beneath the conjunc- 

 tival surface, contributing to their form and support. The superior tarsal plate, superior 

 tarsus, or superior tarsal body (tarsus superior) (Fig. 823), the larger, is of a semilunar form, 

 about 8 mm. (one-third of an inch) in breadth at the centre, and becoming gradually narrowed 

 at each extremity. To the anterior surface of this plate the aponeurosis of the Levator palpebrae 

 is attached. The inferior tarsal plate, inferior tarsus, or inferior tarsal body (tarsus inferior) 



