He was, in truth, acting, play-acting, attempting to do what he had no heart- prompting to do.

He made believe to play, and uttered simulated growls that failed of the verity of simulation.
He bobbed his tail good-naturedly and friendly, and growled ferociously and friendly; but the keenness of the drunkenness of the mate discerned the difference and aroused in him, vaguely, the intuition of difference, of play-acting, of cheating.

Jerry was cheating--out of his heart of consideration.

Borckman drunkenly recognized the cheating without crediting the heart of good behind it.

On the instant he was antagonistic.