How we cite our quotes:
His head was propped up just enough to rest uncomfortably, almost masochistically, against the very base of the headboard. (1.1)
This is a great example of Salinger's eye for physical detail. We know so much about Mr. McArdle's personality and character from the physical characterization in this first paragraph.
"If that bag can't support a ten-year-old boy, who's thirteen pounds underweight for his age, I don't want it in my cabin," Mrs. McArdle said, without opening her eyes. (1.8)
Teddy is mentally and spiritually advanced, yet physically, he is behind for his age. This might be a reminder that the physical body is not an important factor in this story.
"She's adequately covered. I made her wear her dungarees," Teddy said. "Some of them are starting to sink now. In a few minutes, the only place they'll still be floating will be inside my mind. That's quite interesting, because if you look at it a certain way, that's where they started floating in the first place. If I'd never been standing here at all, or if somebody'd come along and sort of chopped my head off right while I was –" (2.19)
It's interesting that Teddy maintains the sort of detachment he preaches to Nicholson, but at the same time is so vehemently interested in the world around him.