BUCK DISCOVERS THE EMOTION OF LOVE.  Although Buck had received attention and friendship while living on the Judge's ranch, he had never experienced true love. It first comes from Skeet who, like "a mother cat washes its kittens," licks and cleanses Buck's wounds. He looks forward to her "ministrations" after a while, and he comes to appreciate his other canine mate, Nig. But it is primarily Thornton from whom Buck receives true loving attention, and Buck soon realizes that he loves his master: To Buck, it seemed like an act of madness to have such emotions for a human.

DEPENDENCY UPON THORNTON.  Buck also comes to realize that he does not like Thornton to be out of his sight, following at his heels if necessary. But he also knows that no master can be permanent, and this arouses his fears.

CALL OF THE WILD.  Buck also discovers a "primordial" call that conflicts with his present life of love and relaxation. It recalls innate desires of freedom and wildness, but Thornton's love continues to draw him back.

LIFE FOR A LIFE.  Buck had saved Thornton's life several times previously--once from a collapsing ledge and another time from a raging stream. Buck never considered his own well-being, risking his own life to save Thornton on each occasion.