. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE OF SIGHT. 851 sensations, and we shall, therefore, have then to consider the mode of production of the visual sensations. 1. The Dioptric Mechanisms of the Eye.—When rays of light proceed from a luminous body they always pass in straight lines, form- ing in their divergence a cone, the apex of which is the luminous body and the base such a plane as may intercept them. So long as the medium is of uniform density rays pass in straight lines
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE OF SIGHT. 851 sensations, and we shall, therefore, have then to consider the mode of production of the visual sensations. 1. The Dioptric Mechanisms of the Eye.—When rays of light proceed from a luminous body they always pass in straight lines, form- ing in their divergence a cone, the apex of which is the luminous body and the base such a plane as may intercept them. So long as the medium is of uniform density rays pass in straight lines, and if they come in contact with an opaque, polished surface they will be reflected, and the angle of reflection is equal to the angle of incidence and lies in the same plane (Pig. 368). If the rays fall perpendicularly to this opaque surface they will be reflected in the same straight line in which they impinged. If the rays fall upon a translucent surface as they emerge from the opposite side they will be found to be bent from their original course. Fig. 370.—Diagram illustrating Refraction. (Landois.) If Si D represent a ray of light passing through water, when it emerges at D into the atmosphere it will he hent away from the perpendicular G D and lie in the direction S D. through the medium, and though they pass out of the medium in a line parallel with that in which the}' entered, yet they are not coincident with it so long as the medium is bounded by. parallel surfaces (Fig. 369). If these rays pass from a rarer to a denser medium they are bent toward the perpendicular at the point of incidence. If they pass from a denser to a rarer medium they are refracted from the perpendicular (Fig. 370). Thus, when an oblique luminous ray passes through a piece of plate- glass its course from the atmosphere is from a rarer to a denser medium, hence it is, in the glass, bent toward the perpendicular; but in passing out it passes from a denser to a rarer medium, hence it is refra
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiol, bookyear1890
