THE EYELIDS AND CONJUNCTIVA. 



707 



being broader near the centre and narrowing towards the angles of the lids. 

 The lower is thinner, much narrower, and more nearly of an uniform breadth 

 throughout. The free or ciliary edge of the cartilages, which is straight, is 

 thicker than any other part. At the inner canthus the cartilages are fixed 

 by the fibrous slips of the tendo palpebrarum (p. 172) ; and at the outer 

 angle they are attached to the malar bone by a fibrous band belonging to the 

 palpebral ligament, and named the external tarsal ligament. 



The palpebral ligament is a fibrous membrane placed beneath the orbicularis 

 muscle, attached peripherally to the margin of the orbit, and internally to 

 the tarsal cartilages near the inner free edge. The membrane is thickest at 

 the outer part of the orbit. 



Meibomian glands. On the ocular surface of each lid are seen from twenty 

 to thirty parallel vertical lines of yellow granules, lying immediately under 

 the conjunctiva! mucous membrane. They are compound sebacious follicles, 



Fig. 457. 



Fig. 457. MEIBOMIAN GLANDS, 

 LACHRYMAL GLAND, &c., AS SKEN 

 FROM THE DEEP SURFACE OF THE 

 EYELIDS OF THE LEFT SIDE. 



a, palpehral conjunctiva ; 1, 

 lachrymal gland ; 2, openings of 

 seven or eight glandular ducts ; 3, 

 upper and lower puncta lachry- 

 inalia ; 6, 6, shut ends of the 

 upper and lower Meihomian glands, 

 of which the openings are indicated 

 along the margins of the eyelids. 



embedded in grooves at the 



back of the taral cartilages ; 



and they open on the free 



margin of the lids by minute 



orifices, generally as many in 



number as the lines of follicles 



themselves. These glands consist of nearly straight excretory tubes, each 



of which is closed at the end, and has numerous small coecal appendages 



projecting from its sides. The tubes are lined by mucous membrane, oil 



the surface of which is a layer of scaly or pavement epithelium cells. 



According to Heinrich Miiller there is likewise a layer of unstriped muscular fibre 

 contained in each eyelid ; that of the upper lid arising from the under surface of the 

 levator palpebrse, that of the lower lid arising from the neighbourhood of the inferior 

 oblique muscle, and each being inserted near the margin of the tarsal cartilage. It 

 may also be mentioned in this place that the same writer describes a layer of unstriped 

 muscle crossing the spheno-maxillary fissure, corresponding to a more largely developed 

 layer found in the extensive aponeurotic part of the orbital wall of various mammalia. 

 This set of fibres has been more particularly described by Turner (H. Miiller, in 

 Zeitschr. f. Wiss. Zool. 1858, p. 541; W. Turner, in Nat. Hist. Eev. 1862, p. 106). 



The eyelashes (cilia) are strong short curved hsirs, arranged in two or 

 more rows along the margin of the lids, at the line of uni >n between the 

 skin and the conjunctival mucous membrane. The lashes of the upper lid, 

 more numerous and longer than the lower, have the convexity of their curve 

 directed downwards and forwards ; whilst those of the lower lid are arched 

 in the opposite direction. Near the inner canthus these hairs are weaker 

 and more scattered. 



3 A 2 



