Ocular refraction and the shadow test . IIII, figure 103 As thus placed, and shown by IIII, figure 103, the square card IIIrepresents that portion of the globe of the eye surrounding the cornea,the circle P, represents the pupil. The two cards I and II, representtwo bands of light composed of parallel rays, lying in fivo p/nncs atright anglfs to cacli otiicr, they pass through the pupil in the meridiansat 90^ and at 180°, and meet at the focus, or point F, which is sup-posed to be at the retina. Through the aid of the simple device just described, and illustra-ted by figure 103,—which every st
Ocular refraction and the shadow test . IIII, figure 103 As thus placed, and shown by IIII, figure 103, the square card IIIrepresents that portion of the globe of the eye surrounding the cornea,the circle P, represents the pupil. The two cards I and II, representtwo bands of light composed of parallel rays, lying in fivo p/nncs atright anglfs to cacli otiicr, they pass through the pupil in the meridiansat 90^ and at 180°, and meet at the focus, or point F, which is sup-posed to be at the retina. Through the aid of the simple device just described, and illustra-ted by figure 103,—which every student is urged to make for himself,—the condition of vision which figure 102 is intended to represent,will be readily understood. The same idea will be used to demon-strate the other conditions of refraction that occur in the eye. In figure 102, the parallel rays traversing the two planes at rightangles to each other, are shown entering the emmetropic eye in thevertical and horizontal meridians. As the eye possesses equal refrac-. 1 Figure 103 {Continuedi ./ tage). II Y S 1 O L O G I C A I, OPTIC
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