. Human physiology : designed for colleges and the higher classes in schools, and for general reading. ormed in the back partof the eye upon the retina, so that the optic nerve expandedthere may carry impressions from them to the brain. This isdone in this way. The rays of light coming from an objectpass through first the cornea, then the aqueous humor, thenthe crystalline lens, and lastly the vitreous humor to the retina,where they, so to speak, daguerreotype the object. The factthat such an image is formed has been often proved by obser-vation on the eyes of animals. If the eye of a rabbit b
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. ormed in the back partof the eye upon the retina, so that the optic nerve expandedthere may carry impressions from them to the brain. This isdone in this way. The rays of light coming from an objectpass through first the cornea, then the aqueous humor, thenthe crystalline lens, and lastly the vitreous humor to the retina,where they, so to speak, daguerreotype the object. The factthat such an image is formed has been often proved by obser-vation on the eyes of animals. If the eye of a rabbit becleansed from the fat and muscles at its back part, and a candle,be held in front of it, you can see the image of the candlethrough the sclerotic coat, formed upon the retina. So if youtake the eye of an ox, and carefully pare off the back part, so THE EYE. 293 Images on the retina inverted. Camera Obscura. as to leave it very thin, a distinct image of any thing placed infront of the eye may be seen at the back part. The imagehowever will be inverted, as represented in Fig. 162. For the FIG. sake of clearness two rays only are represented as coming fromeach of the two ends of the object, a, c. These rays cross eachother in the middle of the eye, those from a being brought toa focus at 6, and those from c at d. As all the other rays,coming from other points in the object, are refracted in thesame manner, a complete inverted picture of it is thus same thing is seen in the instrument called the camera ob-scura. If light be let into a darkened room through a smallaperture in a window srutter, an inverted picture of objectswithout can be seen on a screen, as represented in Fig. 163. FIG. IG3. ^ ^sr
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