. A text-book of physiology : for medical students and physicians . object so as to obtain a clear focus. In a photographiccamera this accommodation or focusing is effected by moving theground glass plate farther away as the object is brought closer to thelens. In the eye the same result is obtained by increasing the curva-ture and therefore the refractive power of the lens. That a changein the lens is the essential factor in accommodation for near objectsis demonstrated by a simple and conclusive experiment devised by 314 THE SPECIAL SENSES. Helmholtz with the aid of what are known as the ima
. A text-book of physiology : for medical students and physicians . object so as to obtain a clear focus. In a photographiccamera this accommodation or focusing is effected by moving theground glass plate farther away as the object is brought closer to thelens. In the eye the same result is obtained by increasing the curva-ture and therefore the refractive power of the lens. That a changein the lens is the essential factor in accommodation for near objectsis demonstrated by a simple and conclusive experiment devised by 314 THE SPECIAL SENSES. Helmholtz with the aid of what are known as the images of Pur-kinje. The principle of this experiment is represented by the dia-gram given in Fig. 129. The eye to be observed is relaxed;that is, gazes into the distance. A lighted candle is held to oneside as represented, and the observer places his eye so as tocatch the light of the candle when reflected from the observed a little practice and under the right conditions of illumina-tion the observer will be able to see three images of the candle re- A B.
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