How does Buck maintain some measure of pride?

Even after Buck is beaten to a bloody pulp, he still angrily faces his captors:

Dazed, suffering intolerable pain from throat and tongue, with the life half throttled out of him, Buck attempted to face his tormentors. But he was thrown down and choked repeatedly, till they succeeded in filing the heavy brass collar from off his neck. Then the rope was removed, and he was flung into a cagelike crate. There he lay for the remainder of the weary night, nursing his wrath and wounded pride. Ch 1