He was about the best teacher I ever had, Mr. Antolini. He was a pretty young guy, not much older than my brother D.B., and you could kid around with him without losing your respect for him. He was the one that finally picked up that boy that jumped out the window I told you about, James Castle. Old Mr. Antolini felt his pulse and all, and then he took off his coat and put it over James Castle and carried him all the way over to the infirmary. He didn't even give a damn if his coat got all bloody.
What does Holden's anecdote illustrate about Mr. Antolini as a character and Holden's relationship with him?