On a new membrane in the eye : being the substance of a lecture delivered at Oxford; before the late meeting of the British Association for the Advancement of Science / by George Hunsley Fielding.

Date:
1832
Catalogue details

Licence: Public Domain Mark

Credit: On a new membrane in the eye : being the substance of a lecture delivered at Oxford; before the late meeting of the British Association for the Advancement of Science / by George Hunsley Fielding. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    12/102 (page 4)
    In describing the Choroid, Sir C. Bell observes — And it has upon its inner surface a pigment, which being sometimes frm, might be taken for a MEMBRANE.* It may, however, be said, that this bright part is the Tapetum. If so, I should be glad to have it defined w^hat is the Tapetum Pf And this ques- tion, simple as it may sound, is not so easy of ♦ Bell, in. 33. f The internal surface, (says Sir C. Bell) of the Choroid coat, has long been called the Tapetum, from its villous or fleecy appearance, when seen through the microscope. This surface, in the adult, is of a brown colour; in veiy young subjects, it is red and bloody ; and when minutely injected, it is like scarlet cloth. It is by this vascular surface or Tapetum, that the black Pigment, which is laid under the expanded Retina, in the human Eye, is secreted.'' In a note, the same Author observes, he cannot conceive how the Pigment should be confounded with the Tapetum. The name of Tape- tum or Tapis was first given by the French Academicians, in their account of the dissection of a lioness. The membrane which is put into the bottom of the Eye, and laid on the Choroides, which we call the Tapetum, was of an Isabella colour, intermixed with a greenish blue. It was easily separable from the Choroides, which remained entire, with its ordinary thickness, after that we had taken away the membrane which forms the Tapetum.''^ Finally, he says—^' In regard to the Choroid coat, we have to under- stand that it consists of two laminae ; the outer and that which is next to the Sclerotic, being the proper Choroid ; the internal lamina the Tunica Ruyschiana: that on the surface of the Ruyschiana there is a pile or fleece which is called the Tapetum; and lastly, that the secretion of this inner surface is a Pigment, which, in the human Eye, has the appropriate name oiPifjmentum nigrum: but, in many animals, it is of a silver, golden, or t Bcir» Anatomy, in. 33.