He seemed to be dying on his feet, when the master whistled.

The sound cut through the rushing of the Asper as a ray of light probes a dark room, shrill, harsh, like the hissing of some incredible snake, and Satan went an uncertain step forward, reeled, almost fell; but the shoulder of the master was at his side lifting up, and the arm of the master was under his chest, raising.

He tried another step; he went on among the trees with his forelegs sprawling and his head drooped as though he were trying to crop grass.

Black Bart did his part to recall that flagging spirit.

Sometimes it was his snarl that startled the black; sometimes he leaped, and his teeth clashed a hair's breadth from Satan's nose.
By degrees the congealing blood flowed freely again through Satan's body; he no longer staggered; and now he lifted a forepaw and struck vaguely at Bart as the wolf-dog leaped.