为何狗狗光脚踏雪不怕冷?
<p>日本一位科学家研究发现，狗之所以能够光脚在雪地上行走自如，而不觉得冷，奥秘之处在于其脚掌上有个内部中央供暖系统，它能让温暖血液流到特定部位，以避免冰冷的地面导致身体受寒。这套机制是利用温暖的含氧血液，将接触到冰冷地面的冷血液加温，然后送回心脏和中央循环系统。在狗的腿部，动脉和脚掌肉垫的静脉十分靠近，从心脏携带到动脉的血流能够轻易将温热传导到温度较低的静脉血管。这种热传导机制让脚掌垫即使暴露在极低温下，也得以保持恒温状态。</p><p><span word="Ever">Ever</span> <span word="wonder">wonder</span> <span word="how">how</span> <span word="dogs">dogs</span> <span word="can">can</span> <span word="walk">walk</span> <span word="barefoot">barefoot</span> <span word="in">in</span> <span word="the">the</span> <span word="snow">snow</span>? <span word="Now">Now</span> <span word="a">a</span> <span word="Japanese">Japanese</span> <span word="scientist">scientist</span> <span word="may">may</span> <span word="have">have</span> <span word="the">the</span> <span word="answer">answer</span> -- <span word="an">an</span> <span word="internal">internal</span> <span word="central">central</span> <span word="heating">heating</span> <span word="system">system</span>.</p><p><span word="The">The</span> <span word="secret">secret</span> <span word="lies">lies</span> <span word="in">in</span> <span word="how">how</span> <span word="dogs">dogs</span> <span word="circulate">circulate</span> <span word="their">their</span> <span word="blood">blood</span> <span word="to">to</span> <span word="prevent">prevent</span> <span word="cold">cold</span> <span word="surfaces">surfaces</span> <span word="from">from</span> <span word="chilling">chilling</span> <span word="the">the</span> <span word="rest">rest</span> <span word="of">of</span> <span word="their">their</span> <span word="bodies">bodies</span>, <span word="according">according</span> <span word="to">to</span> <span word="Hiroyoshi">Hiroyoshi</span> <span word="Ninomiya">Ninomiya</span>, <span word="a">a</span> <span word="professor">professor</span> <span word="at">at</span> <span word="Yamazaki">Yamazaki</span> <span word="Gakuen">Gakuen</span> <span word="University">University</span>, <span word="just">just</span> <span word="west">west</span> <span word="of">of</span> <span word="Tokyo">Tokyo</span>.</p><p><span word="The">The</span> <span word="system">system</span> <span word="uses">uses</span> <span word="warm">warm</span>, <span word="oxygenated">oxygenated</span> <span word="blood">blood</span> <span word="to">to</span> <span word="heat">heat</span> <span word="the">the</span> <span word="cold">cold</span> <span word="blood">blood</span> <span word="that">that</span> <span word="has">has</span> <span word="been">been</span> <span word="in">in</span> <span word="contact">contact</span> <span word="with">with</span> <span word="a">a</span> <span word="cold">cold</span> <span word="surface">surface</span> <span word="before">before</span> <span word="returning">returning</span> <span word="it">it</span> <span word="to">to</span> <span word="the">the</span> <span word="dog">dog</span>'<span word="s">s</span> <span word="heart">heart</span> <span word="and">and</span> <span word="central">central</span> <span word="circulation">circulation</span>.</p><p>"<span word="Dogs">Dogs</span> <span word="exchange">exchange</span> <span word="heat">heat</span> <span word="at">at</span> <span word="the">the</span> <span word="end">end</span> <span word="of">of</span> <span word="their">their</span> <span word="legs">legs</span>. <span word="Arterial">Arterial</span> <span word="blood">blood</span> <span word="flows">flows</span> <span word="to">to</span> <span word="the">the</span> <span word="end">end</span> <span word="of">of</span> <span word="their">their</span> <span word="legs">legs</span> <span word="and">and</span> <span word="then">then</span> <span word="heats">heats</span> <span word="up">up</span> <span word="venous">venous</span> <span word="blood">blood</span> <span word="before">before</span> <span word="returning">returning</span> <span word="it">it</span> <span word="to">to</span> <span word="the">the</span> <span word="heart">heart</span>," <span word="Ninomiya">Ninomiya</span> <span word="said">said</span> <span word="of">of</span> <span word="his">his</span> <span word="findings">findings</span>, <span word="published">published</span> <span word="in">in</span> <span word="the">the</span> <span word="journal">journal</span> <span word="Veterinary">Veterinary</span> <span word="Dermatology">Dermatology</span>.</p><p>"<span word="In">In</span> <span word="other">other</span> <span word="words">words</span>, <span word="they">they</span> <span word="have">have</span> <span word="a">a</span> <span word="heat">heat</span> <span word="exchange">exchange</span> <span word="system">system</span> <span word="in">in</span> <span word="their">their</span> <span word="feet">feet</span>."</p>
页:
[1]