古时候有个伯乐会相马，
写了部相马的经书传天下。
书中讲，好马脖高眼睛亮，
四腿高长蹄子大。
哪知他，生个儿子太愚笨，
读死书，不求甚解糊涂瓜。
有一天，这孩子田里去玩耍，
捉了只特大的蛤蟆捧回家，
“爸爸、爸爸”连声叫，
“快来看，这有一匹最好的马！
像你讲的脑袋像你说的腿，
眼睛明亮圆又大！
别看它皮外无毛疙瘩多，
它可是又能蹦来又会爬！”
伯乐一见心好恼，
可也拿儿子没办法。
“孩子啊，你看问题太简单，
难怪今天闹笑话。
你捉的若是好马就骑试试，
我怕你难以驾驭它！”
这孩子眨巴着双眼开了窍，
一撒手放了那只癞蛤蟆，
让它回田里捉害虫，
消灭害虫保庄稼。
到后来，“按图索骥”作成语，
常比喻，做事拘泥旧成法；
也比喻，寻找事物有线索，
避免盲目乱抓瞎。
Look for a Steed with
the Aid of Its Picture
Once there was an old man by the name of Bo Le，who was quite good at judging horses。He wrote a book on it and it was of great value。If the neck is high and the eyes are bright，it is a very good steed，the book says。If the legs are long and the hooves are big，it is a very good steed，the book says。But the man had a son who was not quite as clever。Though he loved to read，he could hardly grasp anything。One day，while the boy was playing in the fields，he caught hold of a very big toad and went running home。
“Dad，dad，”he called out，“come and take a look，I've got the best steed in the world。The head is tall and the legs are long，the eyes are bright and round and large，just like you wrote in the book。Although he has no hair and has a spotted hide，he can jump and crawl along as well。”
Bo Le become annoyed at what he saw，but there was nothing he could do with his stupid son。
“My dear child，you are very single-minded，no wonder today you made a serious mistake。If it were a good horse，why didn't you get on its back。I fear you could not manage it。”At this the child seemed to understand and let go of the big toad。“Let it go to the corn field to kill the pests who might eat the crops otherwise。”
Hence it came into being this idiomatic phrase。It means“to do just as it is shown to be”，or“in doing something you must try to use common sense，avoiding a blind and careless mistake。”
