Two passages

The beginning of the story is a direct commentary by the narrator. He described the man, his provisions, the weather, and the man's limited experience. He also tells us that the man is "without imagination".

But all this - the mysterious, far-reaching hairline trail, the absence of sun from the sky, the tremendous cold, and the strangeness and weirdness of it all - made no impression on the man. It was not because he was long used to it. He was a new-comer in the land, a _chechaquo_, and this was his first winter. The trouble with him was that he was without imagination. He was quick and alert in the things of life, but only in the things, and not in the significances.

London also provides commentary in his descriptions of the dog's instincts.

The dog did not want to go. It hung back until the man shoved it forward, and then it went quickly across the white, unbroken surface. Suddenly it broke through, floundered to one side, and got away to firmer footing. It had wet its forefeet and legs, and almost immediately the water that clung to it turned to ice. It made quick efforts to lick the ice off its legs, then dropped down in the snow and began to bite out the ice that had formed between the toes. This was a matter of instinct.