File:The human body. A beginner's text-book of anatomy, physiology and hygiene (1884) (14780794544).jpg

Identifier: humanbodybeginne00mart (find matches)
Title: The human body. A beginner's text-book of anatomy, physiology and hygiene ..
Year: 1884 (1880s)
Authors: Martin, H. Newell (Henry Newell), 1848-1896 Martin, Hetty Cary, (from old catalog) joint author
Subjects: Physiology
Publisher: New York, H. Holt and company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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as we look at near or distant things. In per-sons with good eyes (A, Fig. 57), the lens can accuratelyfocus on the retina, images of very distant objects, andalso of things within seven or eight inches of the eye.In other persons (B), the eyeball is too long from frontto back, and the lens cannot focus on the retina therays or lines of light coming from distant objects: suchpersons are short-sighted. They can see very distinctlythings near the eye, but more distant objects seem of an object looked at, depicted on the retina? Why do we see itrightly ? 8. How is a telescope arranged for seeing near or distant objects ?How do our eyes focus what they look at ? What is said of thispower in good eyes ? Why are some eyes short-sighted ? Why areothers long sighted? 230 HYGIENE OF THE EYES. blurred and indistinct. The op()osite defect is long-sight.In those who suffer from it, the eyeball is so flat that thelens cannot focus on the retina rays of liglit comingfrom a near object (C, Fig. 57).
Text Appearing After Image:
Fig. 57.—Diagram illustrating- the path of parallel rays of lig-ht after enteringa healthy, well-shaped eye (A), a short-sighted eye (i5), and a long-sighted eye (C). 9. Hygiene of the Eyes.—Looking directly at verybright objects, as the sun or an electric lamp, dazzlesand injures the eyes; so does sudden change from dark-ness to light. On first waking, the eyes should be some-what gradually accustomed to bright light. The illeffects of such changes are much less serious than theharm that may be done by using the eyes when there isnot enough light to see clearly. Frequent reading or 9. What is the effect on the eyes of looking at very bright lights ?Why should they be gradually accustomed to light after sleeping?What is even more injurious to the eyes than sudden changes from E YEUDS.— TEARS. 231 sewing in such feeble light that the eyes feel strained,will certainly injure them permanently. Long-sight and short-sight are not diseases. Theyare due to the fact that the eyeball is

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