"Do you know how it hurts to have your leg torn off, boy? Do you know, children?"
"No," came in a chorus.
The guide took out a piece of paper and drew a picture on it. "There, every part of that little fellow's body I've drawn has muscles, such fine muscles no naked eye could ever see them. I'll show them to you under the microscope in my cabin. Those muscles move the body, and each muscle is controlled by threads, still more fine, called nerves."
The old man reached out like a flash and pinched Jimmie.
"Ouch!" cried the boy, and there was a shout of laughter from the children.
"You felt that?"
"I guess I did," said Jim, sulkily.
"Well, that's because you're made something the same way this butterfly is. When anything hurts us it's because some of our nerves are hurt, and quick as a flash the news travels to the brain, and we try to get away from the thing that causes pain—a pinch, perhaps, or, still worse, the hurt of a poor leg that has been torn off."
"But a butterfly hasn't any brain," objected Jimmie, who was still cross.
"Hasn't it? Well, we'll see. Now, you watch my pencil." He pointed to the head of the butterfly. "This little fellow has a very tiny brain there. Also running through the body, from end to end, is a little tube through which the food passes. It is in the head above this tube where the tiny brain is, and from which two little threads run down around the tube and join to form another little knot of nerve cells like that of the brain. Then, from this second one there runs a series of little knots united by fine threads the entire length of the body, one in each ring of the body. Do you understand that?"