淘金高阶英语六级巅峰阅读 篇章阅读25：视力研究
<p> 篇章阅读25：视力研究</p><p> <span word="The">The</span> <span word="human">human</span> <span word="criterion">criterion</span> <span word="for">for</span> <span word="perfect">perfect</span> <span word="vision">vision</span> <span word="is">is</span> 20/20 <span word="for">for</span> <span word="reading">reading</span> <span word="the">the</span> <span word="standard">standard</span> <span word="lines">lines</span> <span word="on">on</span> <span word="a">a</span> <span word="Snellen">Snellen</span> <span word="eye">eye</span> <span word="chart">chart</span> <span word="without">without</span> <span word="a">a</span> <span word="hitch">hitch</span>. <span word="The">The</span> <span word="score">score</span> <span word="is">is</span> <span word="determined">determined</span> <span word="by">by</span> <span word="how">how</span> <span word="well">well</span> <span word="you">you</span> <span word="read">read</span> <span word="lines">lines</span> <span word="of">of</span> <span word="letters">letters</span> <span word="of">of</span> <span word="different">different</span> <span word="sizes">sizes</span> <span word="from">from</span> 20 <span word="feet">feet</span> <span word="away">away</span>. <span word="But">But</span> <span word="being">being</span> <span word="able">able</span> <span word="to">to</span> <span word="read">read</span> <span word="the">the</span> <span word="bottom">bottom</span> <span word="line">line</span> <span word="on">on</span> <span word="the">the</span> <span word="eye">eye</span> <span word="chart">chart</span> <span word="does">does</span> <span word="not">not</span> <span word="approximate">approximate</span> <span word="perfection">perfection</span> <span word="as">as</span> <span word="far">far</span> <span word="as">as</span> <span word="other">other</span> <span word="species">species</span> <span word="are">are</span> <span word="concerned">concerned</span>. <span word="Most">Most</span> <span word="birds">birds</span> <span word="would">would</span> <span word="consider">consider</span> <span word="us">us</span> <span word="very">very</span> <span word="visually">visually</span> <span word="handicapped">handicapped</span>. <span word="The">The</span> <span word="hawk">hawk</span>. <span word="for">for</span> <span word="instance">instance</span>, <span word="has">has</span> <span word="such">such</span> <span word="sharp">sharp</span> <span word="eyes">eyes</span> <span word="that">that</span> <span word="it">it</span> <span word="can">can</span> <span word="spot">spot</span> <span word="a">a</span> <span word="dime">dime</span> <span word="on">on</span> <span word="the">the</span> <span word="sidewalk">sidewalk</span> <span word="while">while</span> <span word="perched">perched</span> <span word="on">on</span> <span word="top">top</span> <span word="of">of</span> <span word="the">the</span> <span word="Empire">Empire</span> <span word="State">State</span> <span word="Building">Building</span>+ <span word="It">It</span> <span word="can">can</span> <span word="make">make</span> <span word="fine">fine</span> <span word="visual">visual</span> <span word="distinctions">distinctions</span> <span word="because">because</span> <span word="it">it</span> <span word="is">is</span> <span word="blessed">blessed</span> <span word="with">with</span> <span word="one">one</span> <span word="million">million</span> <span word="cones">cones</span> <span word="per">per</span> <span word="square">square</span> <span word="millimeter">millimeter</span> <span word="in">in</span> <span word="its">its</span> <span word="retina">retina</span>. <span word="And">And</span> <span word="in">in</span> <span word="water">water</span>, <span word="humans">humans</span> <span word="are">are</span> <span word="farsighted">farsighted</span>. <span word="while">while</span> <span word="the">the</span> <span word="kingfisher">kingfisher</span>, <span word="swooping">swooping</span> <span word="down">down</span> <span word="to">to</span> <span word="spear">spear</span> <span word="fish">fish</span>. <span word="can">can</span> <span word="see">see</span> <span word="well">well</span> <span word="in">in</span> <span word="both">both</span> <span word="the">the</span> <span word="air">air</span> <span word="and">and</span> <span word="water">water</span> <span word="because">because</span> <span word="it">it</span> <span word="is">is</span> <span word="endowed">endowed</span> <span word="with">with</span> <span word="two">two</span> <span word="foveae">foveae</span>.-<span word="areas">areas</span> <span word="of">of</span> <span word="the">the</span> <span word="eye">eye</span>, <span word="consisting">consisting</span> <span word="mostly">mostly</span> <span word="of">of</span> <span word="cones">cones</span>. <span word="that">that</span> <span word="provide">provide</span> <span word="visual">visual</span> <span word="distinctions">distinctions</span>. <span word="One">One</span> <span word="fovea">fovea</span> <span word="permits">permits</span> <span word="the">the</span> <span word="bird">bird</span>, <span word="while">while</span> <span word="in">in</span> <span word="the">the</span> <span word="air">air</span>. <span word="to">to</span> <span word="scan">scan</span> <span word="the">the</span> <span word="water">water</span> <span word="below">below</span> <span word="with">with</span> <span word="one">one</span> <span word="eye">eye</span> <span word="at">at</span> <span word="a">a</span> <span word="time">time</span>. <span word="This">This</span> <span word="is">is</span> <span word="called">called</span> <span word="monocular">monocular</span> <span word="vision">vision</span>. <span word="Once">Once</span> <span word="it">it</span> <span word="hits">hits</span> <span word="the">the</span> <span word="water">water</span>, <span word="the">the</span> <span word="other">other</span> <span word="fovea">fovea</span> <span word="joins">joins</span> <span word="in">in</span>, <span word="allowing">allowing</span> <span word="the">the</span> <span word="kingfisher">kingfisher</span> <span word="to">to</span> <span word="focus">focus</span> <span word="both">both</span> <span word="eyes">eyes</span>, <span word="like">like</span> <span word="binoculars">binoculars</span>, <span word="on">on</span> <span word="its">its</span> <span word="prey">prey</span> <span word="at">at</span> <span word="the">the</span> <span word="same">same</span> <span word="time">time</span>. <span word="A">A</span> <span word="frogs">frogs</span> <span word="vision">vision</span> <span word="is">is</span> <span word="distinguished">distinguished</span> <span word="by">by</span> <span word="its">its</span> <span word="ability">ability</span> <span word="to">to</span> <span word="perceive">perceive</span> <span word="things">things</span> <span word="as">as</span> <span word="a">a</span> <span word="constant">constant</span> <span word="motion">motion</span> <span word="picture">picture</span>. <span word="Known">Known</span> <span word="as">as</span> <span word="bug">bug</span> <span word="detectors">detectors</span> , <span word="a">a</span> <span word="highly">highly</span> <span word="developed">developed</span> <span word="set">set</span> <span word="of">of</span> <span word="cells">cells</span> <span word="in">in</span> <span word="a">a</span> <span word="frogs">frogs</span> <span word="eyes">eyes</span> <span word="responds">responds</span> <span word="mainly">mainly</span> <span word="to">to</span> <span word="moving">moving</span> <span word="objects">objects</span>. <span word="So">So</span>, <span word="it">it</span> <span word="is">is</span> <span word="said">said</span> <span word="that">that</span> <span word="a">a</span> <span word="frog">frog</span> <span word="sitting">sitting</span> <span word="in">in</span> <span word="a">a</span> <span word="field">field</span> <span word="of">of</span> <span word="dead">dead</span> <span word="bugs">bugs</span> <span word="wouldn">wouldn</span> <span word="t">t</span> <span word="see">see</span> <span word="them">them</span> <span word="as">as</span> <span word="food">food</span> <span word="and">and</span> <span word="would">would</span> <span word="starve">starve</span>.</p>
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