THE CRYSTALLINE LENS AND ITS CAPSULE. 905 



In the adult the posterior surface is more convex than the anterior ; it is color- 

 less, transparent, and firm in texture. 



In old age it becomes flattened on both surfaces, slightly opaque, of an amber 

 tint, and increases in density. 



The suspensory ligament of the lens is a thin, transparent, membranous struc- 

 ture placed at first between the vitreous body and the ciliary processes of the 

 choroid, and then passing from these same processes to the anterior surface of 

 the lens near its circumference. It assists in retaining the lens in its position. 

 Its outer surface presents a number of folds or plaitings in which the corresponding 

 folds of the ciliary processes are received. These plaitings are arranged round the 

 lens in a radiating form, and are stained by the pigment of the ciliary processes. 

 The suspensory ligament is that part of the hyaloid membrane, which, as described 

 above, is continued forward to the anterior part of the margin of the lens. It is 

 covered on its outer surface by the pars ciliaris, or connective-tissue framework 

 of the retina, prolonged forward from the ora serrata. That portion of this mem- 

 brane which intervenes between the ciliary processes and the capsule of the lens 

 forms part of the boundary of the posterior chamber of the eye. The posterior 

 surface of this layer is turned toward the vitreous humor, being separated from it 

 at the circumference of the lens by a space called the canal of Petit. 



The canal of Petit is about one-tenth of an inch wide. It is bounded in front 

 by the suspensory ligament; behind by the "posterior layer" of the hyaloid 

 membrane, its base being formed by the capsule of the lens. When inflated with 

 air it is sacculated at intervals, owing to the foldings on its anterior surface. 



The arteries of the globe of the eye are the short, long, and anterior ciliary 

 arteries and the arteria centralis retinae. They have been already described (see 

 page 570). 



The ciliary veins are seen on the outer surface of the choroid, and are named, 

 from their arrangement, the vence vorticosa. They converge to four or five 

 equidistant trunks, which pierce the sclerotic midway between the margin of the 

 cornea and the entrance of the optic nerve. Another set of veins accompany the 

 anterior ciliary arteries and open into the ophthalmic vein. 



The ciliary nerves are derived from the nasal branch of the ophthalmic and 

 from the ciliary or ophthalmic ganglion. 



Surgical Anatomy. Foreign bodies frequently get into the conjunctival sac and cause 

 great pain, especially if they come in contact with the corneal surface during the movements of 

 the lid and the eye on each other. The conjunctiva is frequently involved in severe injuries of 

 the eyeball, but is seldom ruptured alone ; the most common form of injury to the conjunctiva 

 alone is from a burn, either from fire, strong acids, or lime. In these cases union is liable to take 

 place between the eyelid and the eyeball. The conjunctiva is often the seat of inflammation 

 arising from many different causes, and the arrangement of the conjunctival vessels should be 

 remembered as affording a means of diagnosis between this condition and injection of the sclero- 

 tic, which is present in inflammations of the deeper structures of the globe. The inflamed con- 

 junctiva is bright red ; the vessels are large and tortuous, and greatest at the circumference, 

 shading off toward the corneal margin ; they anastomose freely and form a dense network, and 

 they can be emptied or displaced by gentle pressure. 



From a surgical point of view the cornea may be regarded as consisting of three layers: (1) 

 of an external epithelial layer, developed from the epiblast, and continuous with the external 

 epithelial covering of the rest of the body, and therefore in its lesions resembling those of the 

 epidermis and superficial layers of the derma ; (2) of the cornea proper, derived from the meso- 

 blast, and associated in its diseases with the fibre-vascular structures of the body; and (3) the 

 posterior elastic layer with its endothelium. also derived from the mesoblast and having the 

 characters of a serous membrane, so that inflammation of it resembles inflammation of the other 

 serous and synovial membranes of the body. 



The cornea contains no blood-vessels, except at its periphery, where numerous delicate 

 loops, derived from the anterior ciliary arteries, may be demonstrated on the anterior surface of 

 the cornea. The rest of the cornea is nourished by lymph, which gains access to the proper sub- 

 stance of the cornea and the posterior layer through the spaces of Fpntana. This lack of a 

 direct blood-supply renders the cornea very apt to inflame in the cachectic and ill-nourished. In 

 cases of granular lids there is a peculiar affection of the cornea, called pannus, in which the 

 anterior layers of the cornea become vascularized, and a rich network of blood-vessels may be 

 seen on the cornea ; and in interstitial keratitis new vessels extend into the cornea, giving it a 

 pinkish hue. to which the term " salmon patch -' is applied. The cornea is richly supplied with 



