866 ORGAXS OF SPECIAL SEXSE 



sends connective-tissue septa l»et\veen the bundles of the ovi'rlying orl)icularis (as 

 just mentioned) going to the skin. In the orbital part of this lid the central con- 

 nective tissue includes also the palpebral fascia, lying here innnediately beneath the 

 orbicularis muscle; l)ut this soon thins off and fades into the more deeply placed 

 levator expansion. This latter is strengthened l)y an extension of the sheath of 

 the su])erior rectus, Vn' -which this nnisclc is (-nal)led to influence the elevation of 

 the lid indirectly. In the lower lid the central coimective tissue similarly consists 

 of palpel)ral fascia, l)lended with a thin tibrous extension of the sheath of the 

 inferior rectus. Innnediately in front of each tarsus is a little loose connective 

 tissue, which contains the large blood-vessels and nerves of the lids. 



The tarsus of each lid is a stiff plate of close connective tissue, with its sur- 

 faces directed anteriorly and posteriorly; in its substance the Meibomian glands 

 are embedded. One tarsal border is free, viz. towards the edge of the lid, the 

 other is attached; the former is straight, while the latter is convex, especially in 

 the upper lid. The length of each tarsus is about twenty millimetres. Its breadth 

 is greatest in the middle of the lid, and becomes gradually smaller towards each 

 canthus, where the tarsi are joined to the outer and inner palpebral ligaments. The 

 breadth of the upper tarsus (10 mm.) is about twice that of the lower. The thick- 

 ness of each is greatest, and its texture closest, at the middle of its length, thin- 

 ning off towards the canthi and towards both l)orders. Into the superior anterior 

 l)order of the upper tarsus the lower layer of the levator expansion is attached, con- 

 sisting of smooth muscle-fibres constituting the superior palpebral muscle of 

 Miiller. In like manner, at the inferior bord(n- of the lower tarsus, bvmdles of 

 smooth muscle fibre are inserted (the inferior palpebral muscle of Miiller), devel- 

 oped in what has l^een regarded as part of the extension of the sheath of the in- 

 ferior rectus. 



The palpebral conjunctiva is firmly adherent to the back of the tarsus; but in 

 the orl)ital ]>art of the lid loose subconjunctival tissue intervenes between it and 

 Miiller' s palpebral muscle. Adenoid tissue occurs in the substance of the conjunc- 

 tiva, especially in its orbital division. Near the upper fornix, the conjunctiva 

 receives expansions of the tendon of the levator palpebrse and of the sheath of the 

 superior rectus, and, at the lower fornix, of the sheath of the inferior rectus. The 

 surface of the tarsal conjunctiva shows small elevations or papillae everywhere; but 

 these are particularly well marked over the attached border of the tarsus. 



Glands of the eyelids.— From its manner of formation the eyelid may be 

 regarded as consisting of two thicknesses of skin, the inner (or posterior) having 

 been doubled l)ack upon the outer at the edge of the lid; thus the cuticle and 

 corium of the skin proper are represented respectively by the conjunctiva and tai'sus 

 of the inner thickness. At the free border of the lid, accordingly, Ave find glands 

 corresponding to the sebaceous and sweat glands of the skin, viz. large sebaceous 

 glands of the cilia ( Zeiss' s glands) and Moll's modified sweat glands. Again^in the 

 inner skin-thickness of the lid, the Meibomian glands of the tarsus are sebaceous, 

 and acino-tul:)ular glands present at the attached border of the tarsus ("Waldeyer's 

 glands) may be reckoned as modified sweat glands. Glands similar in structure to 

 Waldeyer's also occur at the fornix, and are especially altundant near the outer 

 canthus of the upper lid, close to the efferent ducts of the lacln-ymal gland; from 

 tlieir structure, and the character of their secretion, these acinous or acino-tulnilar 

 glands have been termed by Henle ' accessory lachrymal glands.' Other simple 

 tubular glands (Henle), formed merely by the depressions between the papilla^, 

 are best developed in the inner and outer fourths of the tarsal conjunctiva of 

 both lids. 



Blood-vessels.— Tlie arteries run in the central connective tissue of the lids, 

 mainly in tlie form of arches near the borders of the tarsus, from Avhich twigs go 

 to the different pal))el)ral tissues. They are supplied by the lachrymal and j>al])e- 

 l)ral branches of the o])hthalmic, and by small l)ranches derived from the temporal 

 artery. The veins are more numerous and larger than the arteries, and form a 

 close plexus beneath each fornix. They em])ty themselves into the veins of the 

 face at the imier, and into the orbital veins at the outer canthus. 



The lymphatic vessels of the lids are numerous, and are ])rincipally situated 

 in the conjunctiva. Lyniph-si)aces also surround the follicles of the Meibomian 



