Buckmaster's Elements of animal physiology / by John Angell.

  • Angell, John
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Buckmaster's Elements of animal physiology / by John Angell. Source: Wellcome Collection.

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    pensory ligament, which is supposed to permit of the alteration in the shape and position of the lens required for its proper adjustment. (See C, Fig. 84.) The Vitreous Humour or body (from L., vitrum, glass) is the largest lens or humour in the eye. It consists of a perfectly transparent, thin, jelly-like, albiiminoid fluid, enclosed in an extremely thin, delicate, transparent membrane, termed the hyaloid membrane (from Gr., hyalos, glass), and fills 4-5ths of the globe of the eye. It is convex or spherical, except in front, where it is hollowed out into a saucer-shaped cavity to receive the back of the crystalline lens. The hyaloid membrane lines the retina and the back of the crystalline lens, and, according to some writers, sends off delicate lamellce or processes into the interior, which divide it into cells or spaces, which are filled with the clear fluid just described. (See V, Fig. 84.) This fluid consists of about 98 4 per cent, of water, and about I ’6 per cent, of solids, chiefly albumen and common salt. Nature of Light. — Light is one of the im- potiderables; but whether it consists of corpuscles, undulations of ether, or is a mere variety of chemical or physical action, is not yet definitely determined. It moves at the rate of 191,500 miles per second. It always travels in straight lines when passing through the same medium, and when passing perpendictdarly from one medium into another; but when it passes obliquely from one medium into another, its course is broketi, and it is bent out of a straight line, or, in other words, it undergoes refraction (from L., re, back; and frango, I break). When rays of light pass through a convex lens, or magnifying glass, they are bent out of their course, brought to a focus (from ~L., focus, a point), and made to cross each other, thus producing an inverted image, as illustrated by the arrow. Fig. 84. The optical parts of the eye act upon light very similarly to the telescope and the camera obscura, and, like them, require special means of adjustment.