Volume 2

The collected papers of Sir W. Bowman, Bart., F.R.S / edited for the committee of the "Bowman Testimonial Fund" by J. Burdon-Sanderson and J. W. Hulke.

  • Bowman, William, Sir, 1816-1892.
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: The collected papers of Sir W. Bowman, Bart., F.R.S / edited for the committee of the "Bowman Testimonial Fund" by J. Burdon-Sanderson and J. W. Hulke. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    -^-nd to Tp^nd of an inch. These measurements exhibit considerable variety, which it is important for the practical surgeon to be aware of. The first portion of the cornea that comes under our review is the cornea proper, or the lamellated tissue. It is this which forms the greatest proportion of the thickness of the cornea, and gives it strength and toughness. This is bounded externally by a peculiar lamina, the anterior elastic lamina, on which rests the anterior or conjunctival epithelium, and it is bounded behind by another peculiar lamina, the posterior elastic lamina, behind which is the epithelium of the aqueous humor. It is the cornea proper alone which is strictly continuous with the sclerotica. Of the Lamellated Tissue of the Cornea. That the cornea proper is lamellated has long been known, and may be shown in a variety of ways. If a flap be shaped out on its surface by superficial incision and then torn up, the surface of laceration will be nearly parallel to the outer surface, and in this way layer after layer may be removed, especially in the eyes of the larger domestic quadrupeds. The knife, too, especially if blunt, having once pierced this tissue, is found to pass more readily in a horizontal direction, at whatever depth. These are circumstances with which all should render themselves practically familiar, who propose to make the living eye the subject of their operations. This physical construction of the lamellated cornea makes it desirable for the surgeon, when about to penetrate the cornea, to thrust the knife somewhat perpendicularly into it, since the arrangement of the tissue tends to carry the instrument in a horizontal course. The lamellated cornea is tough, unyielding, and almost perfectly transparent ; and it is interesting to study the precise nature of its lamellse, because there are facts which show that its transparency is very easily impaired by any derangement of their relative position, or by an increase of their natural tension. For example, if a thin vertical section of this part be made, and laid upon a slip of glass moistened with water, it remains transparent; but if you attempt to stretch it, in whatever direction, or to compress its parts into a smaller space, it instantly becomes milky and opaque. Again, if you squeeze a fresh and perfect eye between the finger and thumb, the cornea, it is well known, becomes immediately opaque in your hand, but quite recovers itself as you remit the pressure: and in all cases the degree of opacity is proportionate to the pressure you exert. This is a very remarkable experiment, and may serve to illustrate in some measure the opacity or haze of the cornea, which is apt to occur at an early stage of acute internal inflammation of the eyeball, attended with great engorgement of its vessels—a state also elucidated by what occurs in artificial injections of the eye, for when the vessels become gorged, and the globe tense and hard, the cornea invariably grows dim, and shuts off the iris from view.