another, often brownish, and therefore overlooked, and scattered pretty uniformly over a portion or the whole of the cornea. Though these sometimes grow fainter under appropriate treatment, I have never seen them altogether removed.*

Warty opacity of the cornea.-It will readily be conceived that opportunities but seldom offer of submitting specimens of the several forms of opacity to exact scrutiny by the microscope. On this account I shall make no apology for describing the appearances of an opaque spot which occurred on the front of the cornea of an ox, and which I examined in the fresh state. It was about an eighth of an inch across, slightly raised, and densely opaque, and it seemed to have been the result of an ulcer, for the lamellated tissue was involved to a slight depth, and had been replaced by new tissue, as represented in Fig. 6. This new tissue was dense and fibrous, and hardly

FIG. 6.

admitted the light to pass through it even when cut very thin. It contained a large admixture of irregular nuclei and elastic tissue passing in all directions. But what was most remarkable was, that this substitute for the proper corneal tissue was thrown up under the

Vertical section of an opacity of the cornea of an ox. a, new tissue in place of destroyed lamellated tissue papillæ are developed on conjunctival epithelium in it, surmounted by opaque and thick con- the form of numerous pajunctival epithelium, or, as it might be here

called, epidermis. b, healthy lamellated pillæ, arranged in much the tissue below the opaque spot. (Magnified same way as we find them slightly.) in the more highly developed parts of the skin, though apparently without vessels, and of a texture too opaque to be precisely described. The epithelium over these papillæ was likewise opaque and diseased, being composed of a compact aggregation of nucleated particles, which contained numerous opaque granules, and failed to present that regular gradation from the spheroidal to the scaly figure, which is natural in this situation. The extreme surface only was scaly. I cannot help regarding this morbid condition as one of considerable interest, both as a proof of the affinities of the anterior part of the cornea to the integumental

tissues, and as an example of the definite organization of the new materials into persistent forms, opaque and otherwise different from the original structure which they supplant, and incapable of remedy.*

I shall conclude the present lecture with a short description of the structure which replaces the cornea when wholly or partially destroyed, and which is liable to become bulged, so as to constitute the state known as staphyloma corneæ.

The whole thickness of the cornea, in a larger or smaller extent, having perished from any cause, the iris is exposed, and occupies the breach, becoming adherent to the border of the gap formed by the removal of the lost part. If the contents of the globe do not further escape, and the eyeball consequently collapse, time is afforded for reparative processes to take place, by which the opening is filled with new material by granulation. At first this new material is soft, vascular, and nearly on a level with the surrounding parts; and, if nature is allowed to proceed with her operations undisturbed, it gradually acquires firmness, toughness, and considerable density, so as to appear not unlike the original cornea, except that it is opaque. It becomes covered with an epithelium continuous with the conjunctival, just as an ulcer of the skin acquires an investment of cuticle as it heals. This process was first explained by Mr. Wharton Jones, in an able paper published in the MEDICAL GAZETTE, vol. xxi. p. 847.

Now, in some cases, from causes which it is unnecessary for me at present to specify, this cicatrix contracts more or less, and continues to retain the contents of the globe within their proper bounds, the patient experiencing little inconvenience beyond the loss of vision;† but in other instances the new material begins after a time to evince its want of coherence and strength, by bulging slightly under the pressure occasioned by the accumulation of fluid behind it, that is, of course, behind the iris, in the posterior chamber of the eye. Should the projection increase beyond a certain size, it assumes an unsightly appearance, interferes with the movements of the lids, so as at last even to prevent their closure, and, in a word, grows into such a source of annoyance and irritation, that it requires to be got rid of. This is usually done by the knife, and the lens being allowed to escape, the eyeball permanently shrinks to a small size.

* For a case, which has since occurred to me, of warty opacity in the human subject, relieved by shaving it off, see Appendix, Case L.

† Appendix, Case D.

The whole substance of the cicatrix being shaved off from the front of the globe, affords us, now and then, the opportunity of examining its structure in the perfectly recent state, which we can seldom do with any other of the morbid tissues of which this organ is the seat. I had such an opportunity last summer, in the case of a little girl; and the following, in few words, is a description of the structure of the tough opaque membrane which occupied the place of the lost cornea :—Its thickness was very unequal; its posterior surface, to which portions of the iris adhered, being irregularly pitted, or, as it were, worm-eaten; its anterior surface was formed by a thickish coating of epithelium, somewhat resembling cuticle, being composed of eight or ten layers of cells, the deep ones globular, the superficial ones scaly, and more like epidermic cells than those of the healthy cornea. There was no anterior elastic lamina, and no posterior elastic lamina. The entire remaining portion of the thickness of the staphyloma consisted of a dense and most irregular interweaving of white and yellow fibrous tissue, with imperfectly developed nuclei intermingled, and the meshes of the tissues large, unequal, and open on all sides.

FIG. 7.

In this condition we have an eminent example of those results of the reparative action, after loss of substance of the cornea, which we have already had occasion to notice as the consequence of ulcers or

Section of staphyloma; treated with acetic acid: small sloughs, the from a girl. (Slightly magnified.)

chief difference being

that here the new material is derived in a great measure, or wholly, from the vascular iris, rather than from the cornea itself. We see how far the reparative powers fall short of restoring the complex and elaborate structure of the cornea as it is originally laid down in the development of the body. The thickness of the new cuticle is attributable in part to the constant friction of the lids.

42

LECTURE III.

Structure of the choroid coat-its inflammatory products poured out on its inner surface, and why ?-Choroidal epithelium.-Ciliary body and processes. -Course of the needle in the operations on the lens through the sclerotica. Internal structure of the ciliary processes-their influence on the nutrition of the vitreous and lens.-The Iris-description of the iris in an albino.—Contractile tissue.—Vessels and nerves.—Mobility of the iris. Ciliary muscle— ciliary nerves.-' -The Vitreous humor.-Suspensory ligament of the lens—its attachment to the capsule of the lens, with a description of the latter.-Relation of the suspensory ligament to the hyaloid membrane.-Mode of formation of the canal of Petit.-Adjustment of the eye to distinct vision at different distances.

In the preceding lectures I have described to you the structures of the sclerotica and cornea, and have endeavoured to illustrate some of the processes that occur in them in the living subject, both during health and disease. At present I propose to proceed with the parts that lie within the outer case.

Of the internal structures, the most important for the surgical student to acquire an exact knowledge of are, undoubtedly, the iris and the lens, as these both lie full in view, and are often the seat of mechanical hindrances to sight, which it is in the power of the operator

to remove.

To understand the position and arrangement of these two structures it will be necessary for me to speak briefly of the choroid membrane (of which the iris may be regarded as a production), and its ciliary processes, and of the aqueous and vitreous humors.

OF THE CHOROID MEMBRANE.

The delicate choroid membrane, placed within the sclerotica, between that coat and the retina, has, of course, the same general shape

ANATOMY OF THE CHOROID COAT.

43

and curvature that these have. It is essentially a vascular coat, and consists chiefly of blood-vessels, amongst which, however, in most cases an abundant pigment is interspersed in nucleated cells, which diverge into very irregular, often branching, processes, variously inclined as regards the other tissues. A peculiar fibrous tissue is added, which holds ali in place, and confers some little toughness upon the membrane.

If we remove the sclerotica and cornea from a recent human eye under water, we find that the choroid is of a dark sepia colour, slightly adherent to the outer case, near where the optic nerve passes through them both to terminate in the retina, but in the rest of its extent hardly, if at all, united to that dense fibrous membrane; except, indeed, at the anterior margin, where the sclerotica joins the cornea, and where the adhesion of the choroid is of such a kind as to require a separate description afterwards.

The exposed surface of the choroid is slightly flocculent, and some of the pigment easily separates and diffuses itself in the water. The ciliary nerves, which have pierced the sclerotica a little in front of the optic nerve, are seen now taking a forward course (having become flattened), and dividing sparingly into branches till they enter the ciliary muscle, which presents itself as a broad semi-transparent greyish belt intervening between the sclerotica and choroid for about an eighth of an inch all round the cornea. When the choroid has been so fully injected through the ciliary arteries that the fluid has traversed the capillaries, and also the veins, we see its outer surface to be composed of the arterial and venous branches, and its inner surface of the capillaries. The arteries, comparatively small, take a meandering course forwards between the veins, while the veins run in curves, vasa vorticosa, to four or five principal trunks, by which the blood leaves the organ. The capillaries form on the inner surface of the choroid a plane plexus with close meshes, known as the tunica Ruyschiana. This network is closer, i. e. its meshes are smaller in the hinder part than in front, and the vessels finer. It is the most important part of the choroid, because the capillaries are a more important structure than either arteries or veins--more important, I mean, in regard to the function of the membrane, and also as respects its diseases. In no other part of the body are the arteries and veins so separated by a natural disposition from their own capillaries; and it is most interesting to notice, in accordance with this circumstance,