There once lived an old dog. When he was young, he was a great hunter and his master loved him very much. Now, though, he was becoming slow and weak.
One day, the old dog and his master were walking in the forest. The dog saw a pig and chased it. He caught the pig by its ear, but his teeth were weak and the pig got away.
"My teeth were much stronger when I was young," thought the dog. "I hope my master isn't mad."
When the master saw the pig run away, he was angry. "You useless dog!" he shouted. "What will my family eat tonight?"
The dog was sad. "Master," he said, "it is not my fault that I'm old. For many years, I've helped you to feed your family. Am I worth nothing to you now?"
The master realized that he was wrong. "You're right," he said. "I shouldn't blame you for being old. I should praise you for all your years of service."
Catch+（someone）+by + (someone’s)/the+身体部位
Tom caught Janet by her hand=Tom caught by the hand.汤姆抓住珍娜的手。