It was somewhere in the seventies when old Peaceful Harry woke to a realization that gold-hunting and lumbago do not take kindly to one another, and the fact that his pipe and dim-eyed meditation appealed to him more keenly than did his prospector's pick and shovel and pan seemed to imply that he was growing old. He was a silent man, by occupation and by nature, so he said nothing about it; but, like the wild things of prairie and wood, _____________________.

What is the most critical completion of the passage?