In short, he was taking an interest in the game, although a radically different interest from what he had taken with Skipper.
This time his teeth flashed quicker and with deeper intent at the jowl- clutching hand, and, missing, he was seized and flung down the smooth incline harder and farther than before.

He was growing angry, as he clawed back, though he was not conscious of it.

But the mate, being a man, albeit a drunken one, sensed the change in Jerry's attack ere Jerry dreamed there was any change in it.

And not only did Borckman sense it, but it served as a spur to drive him back into primitive beastliness, and to fight to master this puppy as a primitive man, under dissimilar provocation, might have fought with the members of the first litter stolen from a wolf-den among the rocks.
True, Jerry could trace as far back.

His ancient ancestors had been Irish wolf-hounds, and, long before that, the ancestors of the wolf-hounds had been wolves.