Holden's manual of the dissection of the human body / edited by Luther Holden and John Langton.
- Date:
- 1879
Licence: Public Domain Mark
Credit: Holden's manual of the dissection of the human body / edited by Luther Holden and John Langton. Source: Wellcome Collection.
649/712
![The cornea consists of five layers, which are not all composed of the same kind of tissue. The most superficial layer is the conjunctiva]. This consists of several strata of epithelial cells; the deeper ones, the more numerous, are columnar and placed vertically, the superficial ones are flattened scaly epithelium cells, with well-marked nuclei. The second layer is about the tsoq of an inch thick, and consists of a perfectly structureless lamina, which, when peeled off, has a remarkable tendency to curl. Boiling, or the action of acids, does not render it opaque, like the other layers of the cornea. The third layer (cornea proper') consists of translucent connective tissue, upon which the thickness and strength of the cornea mainly depend. The fibres are arranged in layers, about sixty in number. Between the laminae are irregularly branched spaces, called the cell-spaces of the cornea. In these spaces are lodged the corneal corpuscles, with outstanding processes, which communicate freely with each other, and correspond in shape to the spaces within which they lie. In inflammation of the cornea these corpuscles undergo consider- able changes.* The fourth layer is translucent, elastic and brittle^ and may be easily separated from the preceding lamina?. Like the second layer, it is unaffected by boiling or by the action of acids or alkalies, but is somewhat thinner, being from 2 u'u () to of an inch in thickness. It is termed the menihraiLe of DzsngmgL In the sclerotic coat, close to its junction with the cornea, is situated a small oval canal, lined with epithelium, termed the sinus circidaris iridis, or canal of Schlemm (fig. 161). It is probably a venous sinus, for It can always be injected from the arteries. The fifth layer consists of a single layer of polygonal epithelial cells, resembling those which line serous membranes.f In its healthy state the cornea contains no * If fluid be injected very gently into the cornea proper, there may be demon- strated a system of canals, called Recklinghausen's canals, which arc the communica- tions between the corneal corpuscles; but if the fluid It injected more forcibly, il passes in the course of the fibres composing the various laminae of the cornea, which gives the appearance of a number of varicose ami enlarged tu 1 *-■> crossing each other at right angles: these are termed Bowman's corneal tubes. f For a detailed description of the structure see Todd and Bowman, Physio- logical Anatomy.'](https://iiif.wellcomecollection.org/image/b20417780_0649.jp2/full/800%2C/0/default.jpg)
