Lachrymal to lachrymal gland, conjunctiva, and upper eyelid, inosculating with palpebral arteries.

Supra-orbital, supplies levator palpebræ and superior rectus muscles.

Superior and inferior palpebral, supply eyelids.

Nasal, supplies lachrymal sac.

Short ciliary, twelve to fifteen in number, penetrate sclerotic around optic nerve entrance to supply choroid and ciliary processes. Long ciliary, two in number, penetrate sclerotic, pass forward between it and choroid to supply iris, forming circulus iridis major near ciliary margin, and circulus iridis minor, near margin of pupil. Anterior ciliary, spring from muscular branches, perforate sclerotic, and join circulus iridis major.

Arteria centralis retina, obliquely traverses optic nerve to be distributed to retina.

Muscular branches, one superior, one inferior, to ocular muscles. Anterior cerebral, from internal carotid, gives twigs to optic

nerve.

Infra-orbital, from internal maxillary, supplies inferior rectus and inferior oblique muscles and lachrymal gland.

What are the chief lymph-spaces of the eyeball?
The perichoroidal space, between choroid and sclerotic.
Cavity of capsule of Tenon, between eyeball and capsule.
Vaginal space, between optic nerve and sheath.

What veins return the blood from the eye?

The superior and inferior ophthalmic emptying into the cavernous sinus; they also freely anastomose with the facial veins.

Name the nerves of the eye.

Optic or second cranial, nerve of special sense: motor nerves, third, fourth, sixth, and sympathetic filaments.

the

The Ophthalmic division of fifth, supplies general sensation by Lachrymal, to same-named gland, conjunctiva, and skin of upper eyelid; also the following branches:

Frontal

Supra-trochlear
Infra-orbital

Ganglionic.

; and Nasal Long ciliary.
Infra-trochlear.

The sympathetic arises from cavernous and carotid plexus receiving communicating filaments indirectly from spinal nerves, and sending branches to third, fourth, fifth, and sixth nerves; the Jilator fibres (radiating) of iris, ciliary ganglion, muscles of orbit and lids, with walls of arteries, receive their sympathetic nerve supply from this source; the

Short ciliary, numbering about ten, arise from ciliary (ophthalmic) ganglion, and pierce the sclerotic posteriorly, to ramify in sheath of optic nerve, choroid, ciliary muscle, iris, and cornea; the

Ascending branches of the spheno-palatine (Meckel's) ganglion, reaching orbit by spheno-maxillary fi-sure, usually considered to supply only periosteum, are believed by some to go to optic and sixth nerves and ciliary ganglion.

Give a brief description of optic tracts.

The deep origin of the nerve fibres of these tracts are the optic thalami, corpora geniculata, and nates of corpora quadrigemina, which, forming two flattened bands, wind around crus cerebri, to which they are slightly attached, as well as to lamina cinerea and tuber cinereum, and joining in front of latter they form the optic commissure (see page 200 for illustration and more elaborate description).

What course do the nerve fibres pursue in the optic commissure or chiasm?

The most numerous, the decussating fibres, connect the right hemisphere with the left retina, and the left hemisphere with the right retina, occupying the centre of the commissure.

Other fibres (longitudinal, cerebro-retinal) connect each hemisphere with the retina of its own side.

Others (inter-cerebral) pass posteriorly, connecting the two optic

tracts.

Others (inter-retinal) pass anteriorly, connecting the two retina. What are the origin and course of the optic nerves?

They arise on either side from the optic commissure, each passes into the orbit through optic foramen with central artery of retina, which pierces it, and enter eyeball through lamina cribrosa one

tenth inch to nasal side of globe, to aid in forming retina; these nerves are surrounded with a sheath derived from the dura mater between which and nerve is a lymph space communicating with subarachnoid space.

The arched eminences of skin surmounting upper margins of orbits on each side, from which grow several rows of short, obliquely placed hairs; by the attached muscles the eyebrows can partially shut off light from eyes.

What are the eyelids?

Two movable curtains protecting by their closure the eyes from injury; the upper lid is the larger and more movable, having its own elevator muscle; the

Palpebral fissure is the elliptical space between the margins of lids when opened, the internal and external angles being called, respectively, the internal and external canthus, the former being prolonged inward, leaving a triangular space between the lids, the lacus lachrymalis, at the commencement of which is a small elevation on each lid, the lachrymal papilla", whose summit is pierced by a minute opening, the punctum lachrymale3, the commencement of the lachrymal canal.

What structures form the eyelids?

Externally the skin, beneath which is much loose areolar tissue, separating it from the fibres of the orbicularis palpebrarum muscle. The lids retain their shape by means of the so-called tarsal carti

lages-in reality dense connective tissue without cartilage cells— that for the upper lid being semilunar and the larger, that for lower lid elliptical; these structures are connected at their orbital margins with the circumference of the orbit by a fibrous membrane, the tarsal ligaments, while in addition a rounded fibrous cord, the tendo-oculi, passes between the inner angle of cach and the nasal process of superior maxillary bone.

Imbedded in the cartilages are numerous sebaceous glands, the Meibomian glands, discharging their secretion upon the free edge of lids, preventing their adhesion; they number thirty or forty in the upper lid, fewer in the lower lid.

Attached to the free margins of lids is a double or triple row of stiff hairs, curved in each lid so that their convexities meet, preventing interlacing, these are the cilia, or eyelashes; the inner surfaces of lids are lined by a mucous membrane, the conjunctiva.

Their vascular supply is from the palpebral branches of ophthalmic artery anastomosing with contiguous branches of facial.

The nerves are the third, seventh, and sympathetic to muscles, the ophthalmic branch of fifth to skin and conjunctiva.

Describe the conjunctiva.

It is a mucous membrane lining the inner surfaces of the eyelids and reflected thence upon anterior segment of sclerotic, its epithelial layer passing over cornea; the

Palpebral conjunctiva is thick, opaque, vascular, and covered with papillæ, containing numerous glands; at the inner angle of the eye it forms a semilunar fold, the plica semilunaris1 (Fig. 108). The folds formed by the passage of the conjunctiva from lids to eyeball are called the superior and inferior palpebral folds, the former being the deeper; they contain numerous convoluted mucous glands; the

Ocular conjunctiva is thin, transparent, possesses few vessels in health, and is loosely attached to globe by the subconjunctival areolar tissue.

What is the caruncula lachrymalis" (Fig. 108)?

It is a small, conical, reddish body, at inner canthus, occupying the space called the lacus lachrymalis, and is formed of a group of follicles, resembling the Meibomian glands, covered with conjunctiva; from the caruncle project a few slender hairs.

Describe the lachrymal apparatus.

It consists of the lachrymal gland with its ducts, the canaliculi, the lachrymal sac, and the nasal duct. The

Lachrymal gland (Fig. 107) is an oval, compound racemose gland of the size and shape of an almond, lodged in a depression at upper, outer portion of orbit, its concave under surface resting upon the globe of eye, the conjunctiva, superior and external recti muscles intervening; it is held in contact with orbital periosteum by a few fibrous bands. It has six or seven

Ducts (Fig. 107), opening by minute orifices on upper outer half of palpebral conjunctiva near superior retro-tarsal fold. The secretion, or the

Tears, are taken up by the puncta, thence passing through canaliculi into lachrymal sac and nasal duct, thus reaching inferior meatus of nose.

Describe the canaliculi.

They are two minute canals1 about one-half a line in diameter, commencing at the puncta, the superior passing upward, then bending acutely to pass inward to lachrymal sac, the inferior passing downward, then upward and inward; they are lined with. mucous membrane continuous with conjunctiva, and are one-third of an inch long.