Quote 70
Buck was ravenous. The pound and a half of sun-dried salmon, which was his ration for each day, seemed to go nowhere. He never had enough, and suffered from perpetual hunger pangs. (2.20)
Early in the book, Buck’s feelings of hunger are purely physical.
Quote 71
At the end of this day they made a bleak and miserable camp on the shore of Lake Le Barge. Driving snow, a wind that cut like a white-hot knife, and darkness had forced them to grope for a camping place. They could hardly have fared worse. (3.2)
The harsh elements of the natural world contribute to the hardship Buck suffers.
Quote 72
It was no light running now, nor record time, but heavy toil each day, with a heavy load behind. (4.21)
The idea of carrying a weight or load is a part of Buck’s hardship. It begins as a physical load that he carries.