An absent-minded professor was lecturing on anatomy.

一位粗心的教授正在上解剖课。

"To show you more clearly what I mean, I have here a parcel with a dissected frog. I want you to examine it very carefully."

“为了让你们更清楚地理解我所讲的内容，这个包里有一只解剖了的青蛙，你们要仔细地观察。”

The professor unwrapped the parcel and saw that it contained two sandwiches and a hard-bioled egg. Astonished, the professor said, "I was sure I had eaten my lunch, but where is the frog?"

教授打开包，里面竟是两个三明治和一个熟鸡蛋。教授十分惊讶：“我肯定是已经吃过午饭了，可是那只青蛙哪儿去了呢？”