He had degenerated into an animal that could think.

His heart pounded, his pulse beat, his breast heaved; and this internal strife seemed to thunder into his ears.

He was now enacting the tragedy of all crippled, starved, hunted wolves at bay in their dens.

Only his tragedy was infinitely more terrible because he had mind enough to see his plight, his resemblance to a lonely wolf, bloody-fanged, dripping, snarling, fire-eyed in a last instinctive defiance.
Mounted upon the horror of Duane's thought was a watching, listening intensity so supreme that it registered impressions which were creations of his imagination.

He heard stealthy steps that were not there; he saw shadowy moving figures that were only leaves.