696 THE ORGANS OF SENSE. 
upper and lower pieces, which are fixed to the margins of the respective tarsal 
plates. The internal tarsal ligament is a strong band attached to the nasal process 
of the superior maxillary bone directly in front of the lachrymal groove ; it divides 
at the inner canthus into two slips, one for either tarsal plate. 
The eyelids are further strengthened by membranous expansions, termed the 
superior and inferior palpebral ligaments, which extend into them from the margin 
of the orbit. The superior ligament is continuous, along the upper margin of the 
orbit, with the pericranium and with the periosteal lining of the orbit, and blends 
below with the tendon of the levator palpebree superioris. The inferior hegament is 
prolonged from the under edge of the interior tarsal plate to the lower margin of 
the orbit, where it is continuous with the periosteum of the face and orbital floor. 
Externally, the two palpebral ligaments fuse to form the external tarsal lheament, 
while internally they become thinned, and, separating from the internal tarsal 
ligament, are attached to the lachrymal bone behind the lachrymal sac. These two 
palpebral hgaments form a kind of septum or diaphragm, the septum wi 
between the superficial and deep structures of the eyelids; this septum is perforated 
by the vessels and nerves, which extend from the orbital cavity to the face or 
scalp. 
The skin covering the lids is thin and delicate, and is continuous, at their margins, 
with their conjunctival lining. It contains numerous small sweat glands and fine 
hairs, the latter being provided with sebaceous follicles. Branched pigment cells 
are aa in the cutis, and piyment also exists in the deep layers of the epidermis. 
The subcutaneous tissue is loose and devoid of fat, and in it are found the fibres of 
the orbicularis palpebrarum muscl separate bundle of which, termed the 
muscle of Riolan, occupies the margin of the lids behind the ey elashes. The 
Meibomian glands, or glandulie tarsales, are elongated sebaceous glands with numerous 
lateral offshoots ; they are embedded in the -tarsal plates and filled with cubical 
epithelium. Rather more numerous in the upper than in the lower lid, they open 
by small ducts, about 1 mm. in lenzth, along the id margins behind the eyelashes ; 
the ducts are lined by stratified epithelium placed on a basement membrane. 
Between the eyelashes and the muscle of Riolan are two or three rows of modified 
sweat glands, termed the glands of Moll, the blocking of one of the ducts of which 
frequently gives rise to a stye. 
H. Miiller described a layer of non-striped muscle in each lid: in the upper extending from 
the tendon of the levator palpebree superioris to the upper tarsal plate, and in the lower 
connecting the inferior tarsal plate with the inferior oblique muscle. 
The tendon of the levator palpebree superioris divides into three parts—an 
anterior, passing between the bundles of the orbicularis to the deep surface of the 
skin; a middle, attached to the superior tarsal plate; and a posterior, to the fornix 
conjunctive: there is no corresponding muscle in the lower lid. The eyelashes are 
curved, silky hairs, which project from the free margins of the lids; in the upper 
lid they are longer and more numerous than in the lower, and are curved upwards, 
while those of the lower lid are bent downwards. 
Conjunctiva.—This mucous membrane lines the back of the lids (tunica con- 
junctiva palpebrarum) and is continued on to the front of the endl (tunica 
conjunctiva bulbi). The line along which it is reflected on to the globe of the eye 
is termed the fornix conjunctive. The palpebral portion adheres intimately to the 
tarsal plate and presents numerous papille. It is covered by a layer of columnar 
epithelial cells, beneath the bases of which are small flattened cells. Near the 
fornix a number of acino-tubular glands, much more plentiful in the upper than in 
the lower lid, open on to its free surface. The conjunctiva bulbi is thinner than 
that lining the lids, and is loosely attached to the sclera by submucous tissue. The 
plica semilunaris conjunctivee has already been referred to (p. 695). On the cornea 
the conjunctiva is represented merely by the stratified epithelium, already described 
(p. 684). 
Vessels and Nerves.——-The chief arteries of the eyelids are the superior and inferior palpe- 
bral branches of the ophthalmic, which pierce the septum orbitale above and below the internal 
tarsal ligament and run tortuously outwards in the corresponding lid. On reaching the region 
