. Kirkes' handbook of physiology . Fig. 460. -Diagram Representing by Dotted Lines the Alteration in the Shape of the Lens onAccommodation for Near Objects. (E. Landolt.) eve, the type at last becomes indistinct, and cannot be brought into focusby any effort of accommodation, however strong. This limit, which is termedthe near-point, can be determined by the experiment of Scheiner. Twosmall holes not more than 2 mm. apart are pricked in a card with a pin; atany rate their distance from each other must not exceed the diameter of thepupil. The card is held close in front of the eye, and a small
. Kirkes' handbook of physiology . Fig. 460. -Diagram Representing by Dotted Lines the Alteration in the Shape of the Lens onAccommodation for Near Objects. (E. Landolt.) eve, the type at last becomes indistinct, and cannot be brought into focusby any effort of accommodation, however strong. This limit, which is termedthe near-point, can be determined by the experiment of Scheiner. Twosmall holes not more than 2 mm. apart are pricked in a card with a pin; atany rate their distance from each other must not exceed the diameter of thepupil. The card is held close in front of the eye, and a small needle viewed 646 THE SENSES through the pin-holes. At a moderate distance it can be clearly focussed,but when brought nearer, beyond a certain point, the image appears doubleand more or less blurred. This point where the needle ceases to appear singleis the near-point of vision. Its distance from the eye can of course be readily. Fig. 461.—Diagram of Experiment to Ascertain the Minimum Distance of Distinct Vision. measured. It is usually about five or six inches, 12 to 15 cm. In the accom-panying figure, 461, the lens b represents the eye; e, /, the two pin-holes in thecard, nn the retina; a represents the position of the needle. When the needleis at a moderate distance, the two pencils of light coming from e and / arefocussed at a single point on the retina nn. If the needle be brought nearer
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