As I lay there, eyes closed, half awake, I rubbed my elbows with my palms and found that I was rubbing prodigious calluses.

There was no surprise in this.

I accepted the calluses as of long time and a matter of course.
I opened my eyes.

My shelter was a small cave, no more than three feet in height and a dozen in length.

It was very hot in the cave.
Perspiration noduled the entire surface of my body.