There was no resisting that instinct.

The brute felt an enemy, scented the trackers, clamored and struggled and fought, and would not be gainsaid.
"I CAN'T go on," groaned McTeague, his eyes sweeping the horizon behind him, "I'm beat out.

I'm dog tired.

I ain't slept any for two nights." But for all that he roused himself again, saddled the mule, scarcely less exhausted than himself, and pushed on once more over the scorching alkali and under the blazing sun.
From that time on the fear never left him, the spur never ceased to bite, the instinct that goaded him to fight never was dumb; hurry or halt, it was all the same.

On he went, straight on, chasing the receding horizon; flagellated with heat; tortured with thirst; crouching over; looking furtively behind, and at times reaching his hand forward, the fingers prehensile, grasping, as it were, toward the horizon, that always fled before him.
The sun set upon the third day of McTeague's flight, night came on, the stars burned slowly into the cool dark purple of the sky.