蝾螈断腿，为什么能长回来？

If a salamander loses a leg, it grows a new one. 蝾螈断了腿，能再长出一条新的。 Its cells know how to rebuild the missing part. 它的细胞，知道怎么把缺的部分补回来。 In a few weeks, the new leg is ready. 几周之后，新腿就长好了。 It can even fix parts of its heart and eyes. 它连心脏和眼睛，都能修复一部分。 Scientists study it to help human wounds. 科学家研究它，想帮人类治伤。 Humans cannot do this, but salamanders can. 人类做不到，蝾螈却天生就会。