Dissertations by eminent members of the Royal Medical Society.
- Royal Medical Society of Edinburgh
- Date:
- 1892
Licence: Public Domain Mark
Credit: Dissertations by eminent members of the Royal Medical Society. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![brown] necessary is an alteration in the size of the pupil. This opinion was held by Haller, and long after was defended by M. Le Eoi. He brought forward in corroboration the fact that the nearest objects may be viewed with ease and distinctness through a small hole in a card. Moreover, employing an artificial eye, he found that when with a large aperture the images of near objects were confused and ill-defined in its retina, they became very dis- tinct by contracting the aperture. Huygens con- ceived that the crystalline approached the cornea by the pressure of the external muscles, or that the lens might be made more convex by the same action. Dr. Monro made a set of experiments to prove the effect of the orbicularis palpebrarum. He first opened his eyehd wide, and endeavoured to read a book, the letters of which were so near the eye as to be indistinct. He found he could not do it. He then, keeping the head in the same relation to the book, brought the edges of the eyelids within a quarter of an inch of each other, and made an exertion to read. He then found he could see the letters distinctly. He concludes that in this action of the eye the iris, the recti muscles, the two oblique muscles, and the orbicularis palpebrarum have all their share. Dr. Porterfield, after a very full account of all previous opinions, asserts 'that the change in our eyes consists in the motion of the crystalline,' that ' the ligamentum ciliare performs this change,' and likewise increases the convexity of the cornea. His experiments are very numerous, and described with great minuteness. They prove most satisfactorily the incorrectness of Delahire's theory, while they establish the important fact](https://iiif.wellcomecollection.org/image/b21462252_0271.jp2/full/800%2C/0/default.jpg)
