47 O THE EYE. 



this line and covering the entire internal surface ; and (3) a middle 

 layer. 



1 . The cuticular portion of the eyelid consists of a thin epider- 

 mis and a dermis poorly supplied with papillae. Fine lanugo-like hairs 

 with small sebaceous glands and a few sweat-glands are distributed 

 over its entire surface. The cutaneous connective tissue is very 

 loose, contains very few elastic fibers, and is supplied with pigment 

 cells in the superficial layers. At the lid-margin the papillae are 

 well developed and the epidermis is somewhat thickened. The 

 anterior margin supports several rows of larger hairs, the cilia, the 

 posterior row of which possesses, besides the sebaceous glands, 

 modified sweat-glands, the ciliary glands of Moll, which also empty 

 into or near the hair follicles. The ciliary glands are readily distin- 

 guished from the sweat glands ; their tubules are relatively large, 

 often showing alternating large vesicular segments and short narrow 

 segments. A branching of the tubules has also been observed 

 (Huber). The eyelids are further provided with numerous glands, 

 known as the Meibomian or tarsal glands. About thirty of these 

 glands are found in the upper, a slightly smaller number in the lower, 

 lids. They lie within the tissue of the tarsus vertical to the palpebral 

 margin. Each gland consists of a tubular duct, lined by stratified 

 squamous epithelium, beset with numerous simple or branched al- 

 veoli lined by a stratified, cubic epithelium in every respect similar to 

 that lining the alveoli of sebaceous glands. The ducts of these 

 glands terminate at the palpebral margin posterior to the cilia. (See 



Fig- 3 6 4.) 



2. The conjunctival portion of the eyelids is lined by a simple 

 pseudostratified columnar epithelium, possessing two strata of nuclei. 

 This is continuous with the bulbar conjunctiva at the conjunctival 

 fornix, and is characterized by the occasional presence of folds and 

 sulci. Longitudinal folds in the upper portion of the upper lid 

 running parallel with the lid-margin are frequently present. Goblet 

 cells are usually found in the epithelium. According to W. Pfitz- 

 ner (97), the epithelium of the conjunctiva consists of two or three 

 strata of cells, of which the more superficial possess a cuticular 

 margin. Certain structures which have always been regarded as 

 goblet cells are in all probability similar to the cells of Leydig i. <?., 

 mucous cells, which do not pour their secretion out over the sur- 

 face of the epithelium. Some lymphoid tissue is always found in 

 the stratum proprium of the mucous membrane, and occasionally it 

 is seen to form true lymph-nodules. It is of some interest to note 

 that a marked production of these lymph-nodules occurs in certain 

 diseases. Such lymph-nodules are usually associated with epithe- 

 lial crypts, which fact led Henle to regard them as glandular forma- 

 tions. Small glands with a structure similar to that of the lacrimal 

 glands are also present in the palpebral conjunctiva ; they are known 

 as accessory lacrimal glands and are found in the upper eyelid, at the 

 outer angle of the conjunctival fornix. Similar glands occur also at 

 the mesial angde of the fornix. 



