Spectacle secrets / [George Cox].

  • Cox, George
Date:
[1844]
Catalogue details

Licence: Public Domain Mark

Credit: Spectacle secrets / [George Cox]. Source: Wellcome Collection.

    16/76 page 6
    one of our most sensitive and easily deranged organs. The human eye is composed of a series of humours and membranes: the outer coating, called the sclerotica (a), see Plate, Fig. 1, is exceedingly strong, and the muscles which move the eye are attached to it; the white of the eye is a portion of this coating. The cornea fbj arches out or projects from the eye-ball; it is transparent, and of a circular form. The next coating to the sclerotica is called the choroides (c) ; it has no muscular motion except at its extremities, near the front of the eye. The iris fdj is next apparent; it attaches itself to the sclero¬ tica by a cellular substance called the ciliary circle fej. According to the colour of the iris the eye is termed black, blue, hazel, &c. It is composed of two sets of muscular fibres, the one tending, like radii, towards a centre, the other forming a number of circles concen¬ tric with the same centre. The aperture in the iris is called the pupil (f) ; it is always round, but varies in diameter as the radial or the circular fibres of the iris are contracted or expanded, according to the quantity and quality of light it is required to admit, acting like a watchful centinel to regulate the amount of rays requisite to transmit a perfect and well-defined image of objects onwards to the brain, which, without its agency, would appear one undistinguishable mass of confusion. The chamber of the eye is darkened by the posterior surface of the choroid membrane having a lining of dark-coloured mucus, called the pigmentum nigrum. The last coating of the eye is the retina (g), a delicate and most important membrane in the construction of this noble instrument; it is an expansion of the optic nerve fh), directly emanating from the brain; and is spread like a net of exquisite delicacy all over the surface of the choroides,
    digitised image 1
    digitised image 2
    digitised image 3