On long, short, and weak sight : and their treatment, by the scientific use of spectacles / by J. Soelberg Wells.

  • Wells, J. Soelberg (John Soelberg), -1879
Date:
1862
Catalogue details

Licence: Public Domain Mark

Credit: On long, short, and weak sight : and their treatment, by the scientific use of spectacles / by J. Soelberg Wells. Source: Wellcome Collection.

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    ling the iris, which was before slightly bent, (vide Fig. 2) by the action of the elastic fibres of the ligamentum pectinatum (pillars of the iris), and laid along the whole breadth of the canal of Schlemm against the inner wall of the latter. Besides this, Helmholtz also assumes that the ciliary muscle not only draws the insertion of the iris backwards, but also draws the posterior ends of the ciliary processes forwards, thus causing a relaxation of the zonula, which in its turn again favours the increase in the thickness of the lens. Heinrich Miiller attaches far greater importance to the action of the ciliary muscle than to the iris. He, moreover, discovered that the ciliary muscle consists of two different sets of fibres—a radiating longitudinal and a circular. (Vide Fig. 4, m c i, and m c i^) He ascribes a different action to each set of fibres, and has come to the following conclusions as to the probable action of the difierent parts concerned m accommodation. He thinks that'— 1. The circular fibres of the ciliary muscle exert a pressure upon the edge of the lens, by means of which the latter becomes thicker. • 2. The longitudinal fibres of the muscle cause an increase of tension in the vitreous humoiu, on accotmt of which the posterior surface of the lens is prevented from shiftmg, and the action of the peripheral pressure is chiefly confined to the anterior surface. 3. The pressure of the tense iris on the peripheral portion of the anterior surface of the lens assists in increasing the convexity (arching forward) of the latter, and in preventing the archmg of the posterior surface. * Von Grsefe's Archiv., III., ], 23.
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