I want it in your left arm

An old man went to the hospital. When the doctor came to see him, he said, "Well, Mr.Jones, you're going to have some injection, and then you'll feel much better. 

A nurse will come and give you the first one this evening, and then you'll get another one tomorrow morning.

In the evening a young nurse came to Mr.Jone's bed and said to him, "I'm going to give you your first injection now, Mr.Jones. Where do you want it?

The old man was surpried. He looked at the nurse for several seconds, and then he said, " Nobody's ever let me choose that before. Are you really going to let me choose now?"

"Yes, Mr.Jones," the nurse answered. She was in a hurry, "Where do you want it?"

"Well then," the old man answered with a smile, "I want it your left arm, please."