There was expectancy in David's voice.
"You mean, I suppose—that is—"
"Yes, yes! You know!" David gravely wagged his head.
The Doctor took off his hat and wiped his forehead with his handkerchief.
"If you were a little more definite—not quite so vague and uncertain," he hopelessly suggested.
It was then that a sudden inspiration saved the day for him. He began to talk in a big and solemn voice.
"I perceive, sir," he said, "that you have reached the age for being waylaid. You are four years old, and by an ancient decree of all the Medes and Persians, that makes you my prisoner, to hold in hostage until that ungracious dame, your mother, shall subscribe unto me suitable and sufficient ransom."
David clapped his hands gleefully.
"Go on!" he demanded. "Go on! Now what?"
"Well, when you have all that said to you, it means that if you find a doctor skulking about within ten feet of you, it is then your perfect right to press him into your service. If you command him to give you a ride on his back, he will have to do it. It's undignified and he doesn't believe in it, but that's where you have him at your mercy. He has to obey; he has to go any place you tell him to go. If you say he must take you to a toy shop, that settles it. He has no choice in the matter. He has to do it. That is always the rule when a little boy is four years old."