CHAPTER XLIV.
SENSE OF VISION.
890. This sense contributes more to the enjoyment and happiness of man than any other of the senses. By it we perceive the form, color, volume, and position of objects that surround us. The eye is the organ of sight, or vision, and its mechanism is so wonderful, that it not only proves the existence of a great First Cause, but perhaps, more than other organs, the design of the Creator to mingle pleasure with our existence.
ANATOMY OF THE ORGANS OF VISION.
891. The apparatus of vision consists of the Op´tic Nerve, the Globe and Muscles of the eye, and its Protecting Organs.
892. The OPTIC NERVE arises by two roots from the central portion of the base of the brain. The two nerves approach each other, as they proceed forward, and some of the fibres of each cross to the nerve of the opposite side. They then diverge, and enter the globe of the eyes at their back part, where they expand, and form a soft, whitish membrane.
893. The GLOBE, or ball of the eye, is an optical instrument of the most perfect construction. The sides of the globes are composed of Coats, or membranes. The interior of the globe is filled with refracting Humors, or me´di-ums.
890. Which sense contributes most to the enjoyment of man? What do we perceive by this sense? What is said of the mechanism of the eye? 891–916. Give the anatomy of the organs of vision. 891. Of what does the apparatus of vision consist? 892. Describe the optic nerve. 893. Describe the globe of the eye.