The hand-book of household scienceA popular account of heat, light, air, aliment, and cleansing, in their scientific principles and domestic . rom the Latin cornu, which signi-fies horn. The general arrangement of the parts we are describing isshown in the accompanying view of the section of the eye (Fig. 55). 233. The Iris and Pnpil, and their uses.—Behind the corneathere is a small space or chamber filled with a perfectly clear and col-orless liquid, which consists chiefly of pure water, and is called theaqueous humor. This chamber is divided by a thin partition knownas the zm,
The hand-book of household scienceA popular account of heat, light, air, aliment, and cleansing, in their scientific principles and domestic . rom the Latin cornu, which signi-fies horn. The general arrangement of the parts we are describing isshown in the accompanying view of the section of the eye (Fig. 55). 233. The Iris and Pnpil, and their uses.—Behind the corneathere is a small space or chamber filled with a perfectly clear and col-orless liquid, which consists chiefly of pure water, and is called theaqueous humor. This chamber is divided by a thin partition knownas the zm, in the centre of which there is a circular aperture calledthe pupil. The pupil is simply, therefore, a hole through the iris; itis the round black spot which we see surrounded by a colored colored ring is the iris. It is black behind, and on the frontor visible side, it is of different colors in different individuals. Thecolor of the iris is observed to be, in some measure, connected withthe color of the hair. The iris has the remarkable property of con- 128 STEUCrUEE AND OIIICAL POWEES OF THE EYE. PosteriorcUarnier FlQ. Cernea tracting aud dilating under tlie influence of light, by which the pupUis enlarged aud diminished. If the light be strong, the iris contractsaud reduces the size of the pupil, so as to exclude a portion of the light; if the liglit be weak, the irisexpands so that more light is ad-mitted. This moderates and equal-izes the illumination of the organ,the delicate sensibility of whichmight otherwise be injured. Theplay of this mechanism may easilybe seen by bringing a candle near tothe eye while gazing upon its im-Eelation and names of the seyeral parts age in a locking-glass. These move-of the Eye. ments are involuntary, the eye reg- ulating the quantity of light it will receive, independent of the choiceof the mind, 234. Crystalline Lens and Vltreons Hnmor.—Behind the little chamber,of which we have spoken, and bounding it on
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