Volume 1

Lectures on the parts concerned in the operations on the eye, and on the structure of the retina ... To which are added, a paper on the vitreous humor; and also a few cases of ophthalmic disease / By William Bowman.

  • Bowman, William, Sir, 1816-1892.
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the parts concerned in the operations on the eye, and on the structure of the retina ... To which are added, a paper on the vitreous humor; and also a few cases of ophthalmic disease / By William Bowman. Source: Wellcome Collection.

    28/180 (page 12)
    section, somewhere about sixty mtervene between any two corre- sponding points on the opposite surfaces of the tissue. There is a fact of some interest to be learnt from such a section, if it be made extremely thin, and it is this:—that the connections be-., tween the horizontally-extended lamelle of the cornea are themselves membranous or lamelliform, and not mere fibres; for on opening out the lamellze, so as to enlarge their interspaces, very delicate membranes are seen passing from one to another, and it is but rarely that complete perforations exist, however thin the section have been made. In such specimens, viewed under a high power, we have a faintly fibrous texture apparent in even the mos¢ delicate of these films of mem- brane, the fibrous elements being held together in that form by an homogeneous intervening substance. The nature of the ¢vterstices of the corneal tissue does not appear to have been particularly inquired mto. It has been generally con- sidered that the interlamellar spaces are themselves flattened or lamelliform, and that they contain fluid in sufficient quantity to fall easily from one part to another; and it has been imagined that in- flammatory products, lymph or pus, might gravitate in such natural spaces to the most dependent part of the cornea. or the existence of fluid, stress has been justly laid on the fact, that if we lay bare the corneal tissue and make strong pressure on the globe, we shall ob- serve first a dewy moisture, and then distinct drops of transparent fluid over the entire surface. But this shews the porosity of the entire cornea, rather than the existence of free fluid in its interspaces ; for in the perfectly fresh eye the dew does not form until the pressure has been kept up for some time, and under continued pressure the aqueous humor gradually passes out ; while if this humor have been previously evacuated by puncture and replaced by air, no dew forms upon the surface. Moreover, an incision into the lamellated cornea does not set free any visible fluid. It has been sometimes thought that pressure produces opacity of the cornea, by driving out fluid from its interstices; but the return of transparency is so simultaneous over the whole surface, when the pressure 1s remitted, as to forbid the supposition of any fluid having escaped and re-entered at the border, while the presence or absence of the aqueous humor does not affect the result at all: pressure pro- duces opacity if the chambers are filled with air. Hence it may be