There are no more uses of "prostrate" in the book.
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Francis chose to make it his cross to bear in life; he never understood why his Uncle Atticus remained on excellent but remote terms with his father—Francis thought Atticus should Do Something—or why his mother was not prostrate from his father’s eccentric, therefore unforgivable, behavior.
Harper Lee -- Go Set a Watchman
He sat down on the edge of the bed and softly kicked Colin’s prostrate body.