At such times he would shake off sleep and creep through the chill to the flap of the tent, where he would stand and listen to the sound of his master's breathing.
But in spite of this great love he bore John Thornton, which seemed to bespeak the soft civilizing influence, the strain of the primitive, which the Northland had aroused in him, remained alive and active.
Faithfulness and devotion, things born of fire and roof, were his; yet he retained his wildness and wiliness.

He was a thing of the wild, come in from the wild to sit by John Thornton's fire, rather than a dog of the soft Southland stamped with the marks of generations of civilization.

Because of his very great love, he could not steal from this man, but from any other man, in any other camp, he did not hesitate an instant; while the cunning with which he stole enabled him to escape detection.
His face and body were scored by the teeth of many dogs, and he fought as fiercely as ever and more shrewdly.

Skeet and Nig were too good-natured for quarrelling,--besides, they belonged to John Thornton; but the strange dog, no matter what the breed or valor, swiftly acknowledged Buck's supremacy or found himself struggling for life with a terrible antagonist.

And Buck was merciless.