. The animans and man; an elementary textbook of zoology and human physiology. d important muscleprocesses called ciliaryprocesses (Cp), which,with the suspensory lig-ament (SL) hold the lensin place. Within the choroidcoat is the third andinnermost coat, called FIG. 185. Horizontal section of the eye- , . ~, ball. S, sclerotie coat; ch, choroid coat; the retina (R) • he R, retina; O, optic nerve; Cp, ciliary retina is Composed of processes; Cm, ciliary muscles; L, lens; sensory nerve endings C, cornea; I, iris; S. L, suspensory . ligament. (After Brubaker.) that are Sensitive to light. The fi
. The animans and man; an elementary textbook of zoology and human physiology. d important muscleprocesses called ciliaryprocesses (Cp), which,with the suspensory lig-ament (SL) hold the lensin place. Within the choroidcoat is the third andinnermost coat, called FIG. 185. Horizontal section of the eye- , . ~, ball. S, sclerotie coat; ch, choroid coat; the retina (R) • he R, retina; O, optic nerve; Cp, ciliary retina is Composed of processes; Cm, ciliary muscles; L, lens; sensory nerve endings C, cornea; I, iris; S. L, suspensory . ligament. (After Brubaker.) that are Sensitive to light. The fibers from these nerve cells pass backward to the brain through theoptic nerve (O). Behind the iris lies the crystalline lens (fig. 185, L). Itsfront surface is slightly flattened. The space betweenthe lens and the cornea is filled with a clear transparentliquid, the aqueous humor. The cavity of the eyeball backof the lens is also filled with a transparent semi-solid orjelly-like substance called the vitreous humor. Functions of the eye.—In general structure, the human. SPECIAL SENSES 373 eye is like a camera. The cornea and lens of the eye cor-respond to the lens of the camera, and the retina correspondsto the sensitive plate. The pupil of the iris determines the amount of light thatshall enter the eye. How a lens forms an image. — A ray of light passingfrom a rarer to a denser medium is bent or refracted froma straight line. Therefore rays of light when they enter aconvex lens as shown in fig. 186, are bent so that they allconverge at point A behind the lens, that is, they come to afocus at this point. Thus rays of light from the arrowA — B passingthrough the lensform a picture onthe retina at b — a. Accommodationof the eye to differentdistances. — A photo-grapher changes the B IG- 1^6- Refraction of rays of light and for- matiotn of an ima§e on the ^ina- A;B; ob; ject; b-a, image on retina. (After Brubaker.)
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Keywords: ., bookcentury1900, bookd, booksubjectphysiology, booksubjectzoology
