I 



THE ACCESSORY ORGANS OF THE EYE 1025 



of the facia bulbi, which he has named the suspensory ligament of the eye. It is 

 slung like a hammock below the eyeball, being expanded in the center, and narrow 

 at its extremities which are attached to the zygomatic and lacrimal bones 

 respectively. 1 



The Orbital Fascia forms the periosteum of the orbit. It is loosely connected 

 to the bones and can be readily separated from them. Behind, it is united with 

 the dura mater by processes which pass through the optic foramen and superior 

 orbital fissure, and with the sheath of the optic nerve. In front, it is connected 

 with the periosteum at the margin of the orbit, and sends off a process which 

 assists in forming the orbital septum. From it two processes are given off; one to 

 enclose the lacrimal gland, the other to hold the pulley of the Obliquus superior in 

 position . 



The Eyebrows (supercilia) are two arched eminences of integument, which sur- 

 mount the upper circumference of the orbits, and support numerous short, thick 

 hairs, directed obliquely on the surface. The eyebrows consist of thickened integu- 

 ment, connected beneath with the Orbicularis oculi, Gorrugator, and Frontalis 

 muscles. 



. The Eyelids (palpebrce) are two thin, movable folds, placed in front of the eye, 

 protecting it from injury by their closure. The upper eyelid is the larger, and the 

 more movable of the two, and is furnished with an elevator muscle, the Levator 

 palpebrae superioris. When the eyelids are open, an elliptical space, the palpebral 

 fissure (rima palpebrarum), is left between their margins, the angles of which corre- 

 spond to the junctions of the upper and lower eyelids, and are called the palpebral 

 commissures or canthi. 



The lateral palpebral commissure (commissura palpebrarum lateralis; external 

 canthus} is more acute than the medial, and the eyelids here lie in close contact 

 with the bulb of the eye: but the medial palpebral commissure (commissura 

 palpebrarum medialis; internal canthus} is prolonged for a short distance toward the 

 nose, and the two eyelids are separated by a triangular space, the lacus lacrimalis 

 (Fig. 892). At the basal angles of the lacus lacrimalis, on the margin of each 

 eyelid, is a small conical elevation, the lacrimal papilla, the apex of which is pierced 

 by a small orifice, the punctum lacrimale, the commencement of the lacrimal duct. 



The eyelashes (cilia] are attached to the free edges of the eyelids ; they are short, 

 thick, curved hairs, arranged in a double or triple row: those of the upper eyelid, 

 more numerous and longer than those of the lower, curve upward; those of the lower 

 eyelid curve downward, so that they do not interlace in closing the lids. Near 

 the attachment of the eyelashes are the openings of a number of glands, the ciliary 

 glands, arranged in several rows close to the free margin of the lid; they are regarded 

 as enlarged and modified sudoriferous glands. 



Structure of the Eyelids. The eyelids are composed of the following structures taken in their 

 oriier from without inward: integument, areolar tissue, fibers of the Orbicularis oculi, tarsus, 

 orbital septum, tarsal glands and conjunctiva. The upper eyelid has, in addition, the aponeu- 

 rosis of the Levator palpebrse superioris (Fig. 893). 



The integument is extremely thin, and continuous at the margins of the eyelids with the con- 

 junctiva. 



The subcutaneous areolar tissue is very lax and delicate, and seldom contains any fat. 



The palpebral fibers of the Orbicularis oculi are thin, pale in color, and possess an involuntary 

 action. 



The tarsi (tarsal plates) (Fig. 894) are two thin, elongated plates of dense connective tissue, 

 about 2.5 cm. in length; one is placed in each eyelid, and contributes to its form and support. 

 The superior tarsus (tarsus superior; superior tar sal plate), the larger, is of a semilunar form, about 

 10 mm. in breadth at the center, and gradually narrowing toward its extremities. To the 

 anterior surface of this plate the aponeurosis of the Levator palpebrse superioris is attached. The 

 inferior tarsus (tarsus inferior; inferior tarsal plate), the smaller, is thin, elliptical in form, and 



1 C. B. Lockwood, Journal of Anatomy and Physiology, vol. xx. 

 fcl 



