SUPERIOR FORNIX 



THE APPENDAGES OF THE EYE 1117 



with the lining membrane of the ducts of the Meibomian glands, and, through the 

 lacrimal canals, with the lining membrane of the lacrimal sac and nasal duct. 

 At the outer angle of the upper lid the lacrimal ducts open on its free surface; 

 and .g^^ie^nner angle of the eye it forms n. spmi'lnna.r fnld ; the plica semi lunar is 

 (plica semilunaris conjunctivae) (Fig. 828). The folds formed by the reflection 

 of the conjunctiva from the lids on to the eye are called the superior and inferior 

 palpebral folds, the former being the deeper of the two. These folds form the 

 superior and inferior conjunctival fornix (Fig. 825). 



The Bulbar Portion (tunica conjunctiva bulbi). Upon the sclera the conjunc- 

 tiva is loosely connected to the globe; it becomes thinner, loses its papillary struc- 

 ture, is transparent, and only slightly vascular in health. Upon the cornea the con- 

 junctiva consists onlv, of epithelium, constituting the 

 anterior layer of the cornea (conjunctival epithelium) 

 already described (p. 1093). Lymphatics arise in the 

 conjunctiva in a delicate zone around the cornea, from 

 which the vessels run to the ocular conjunctiva. 



Fornices of Conjunctiva. At the line of reflection of 

 each fold of the conjunctiva from each lid on to the globe 

 of the eye a pocket or arch is formed. These arches are 

 termed the fornices conjunctivae, superior and inferior 



FIG. 825. Sagittal section 



Glands of Conjunctiva. In the conjunctiva there are of eye, showing superior and 



i P i i i i inferior fornices of the con- 



a number or mucous glands which are much convo- junctiva. (Testut.) 

 luted. They are chiefly found in the upper lid. Other 



glands, analogous to lymphoid follicles, and called by Henle trachoma glands, 

 are found in the conjunctiva, and, according to Stromeyer, are chiefly situated 

 near the inner canthus of the eye. They were first described by Brush, who, in 

 his description of Peyer's patches of the small intestines, called them "identical 

 with structures existing in the under eyelid of the ox." 



The caruncula lacrimalis is a small, reddish, conical-shaped body, situated at 

 the inner canthus of the eye, and filling up the small triangular space in this situ- 

 ation, the lacus lacrimalis. It consists of a.n island of skin confainin<y sphanpmis 

 .and sweat glands, and is the source of the whitish secretion which constantly 

 collects at the inner angle of the eye. A few slender hairs are attached to its 

 surface. On the outer side of the caruncula is a slight semilunar fold of conjunc- 

 tiva, the concavity of which is directed toward the cornea; it is called the plica 

 semilunariq (Fig. 828). Miiller found smooth muscle fibres in this fold, and in 

 some of the domesticated animals a thin plate of dense white fibrous tissue has 

 been discovered. This structure is considered to be the rudiment of the third 

 evelid in birds, the membrana nictitans. 



The nerves in the conjunctiva are numerous and form rich plexuses. Accord- 

 ing to Krause they terminate in a peculiar form of tactile corpuscle, the "terminal 

 bulb." 



The Lacrimal Apparatus (apparatus lacrimalis) (Figs. 826 and 828) consists of 

 the lacrimal gland, which secretes the tears, and its excretory ducts, which con- 

 vey the fluid to the surface of the eye. This fluid is carried away by the lacrimal 

 canals into the lacrimal sac, and along the nasal duct into the cavity of the nose. 



The Lacrimal Gland (glandula lacrimalis) is lodged in a depression at the outer 

 angle of the orbit, on the I'nnpr sidp nf flip pvt.prna.1 angular process of t.hp frontal 

 bone. It is of an oval form, about the size and shape of an almond. Its upper 

 convex surface is in contact with the periosteum of the orbit, to which it is con- 

 nected by a few fibrous bands. Its under concave surface rests upon the convexity 

 of the eyeball and upon the Superior and External reoti muscles. Its vessels 

 and nerves enter its posterior border, while its anterior margin is closely adherent 



