Buck
Quote 1
And each time the joyful bark that trembled in Buck's throat was twisted into a savage growl. (1.22)
Immediately after his capture, Buck’s domestic qualities give way to become more primitive.
Buck
Quote 2
With a roar that was almost lionlike in its ferocity, he again hurled himself at the man. (1.32)
The more Buck is provoked, the more he reverts to his primitive nature.
Buck
Quote 3
That club was a revelation. It was his introduction to the reign of primitive law, and he met the introduction halfway. The facts of life took on a fiercer aspect; and while he faced that aspect uncowed, he faced it with all the latent cunning of his nature aroused. (1.40)
Buck discovers latent qualities in himself that he previously did not know he had.