To this rule there was one exception. Warrigal ran steadily in the shadow cast by Finn's big, gaunt frame, her muzzle about level with his elbow. Black-tip kept about the same level on Finn's other side, but a good deal farther off, and the others straggled in fan-shaped formation to the rear, scouting at times to one side or the other in quest of insects and snakes, or any other living thing that fangs could crush. As to digestion, the pack had no concern regarding any such detail as this. Their one test of edibility was swallowing. They even helped Finn to demolish a native porcupine, than which one would have said no creature of a less edible sort was ever created. Altogether, there was that about the survivors of the Mount Desolation pack which would have made any single creature sorry to cross their path, however powerful he might be. No animal with flesh on its bones and blood in its veins would have been too big or fierce for the pack to have attacked just now; for hunger and thirst had made them quite desperate. It was Black-tip, and not Finn, who, on the afternoon of the second day of the pack's despairing return journey in quest of the river-bank they had left a fortnight before, called a sudden halt. (The dingo's sense of smell was always keener than the Wolfhound's.) Black-tip sniffed hard and long at the ground between his fore-feet, and then, raising his head, glared out into the afternoon sunlight to the south-eastward of the track they were following--their own trail. The whimper which escaped Black-tip when he began to sniff, brought the rest of the pack about him, full of hungry eagerness to know what thing it was that had been found. There was something uncanny and extraordinary about the way in which they glanced one at another, after, as it were, taking one sip of the scent which had brought Black-tip to a standstill. Had the scent been of kangaroo or wallaby, rabbit, rat, or any other thing that moves upon four legs, those curious glances would never have been exchanged. The pack would have been off hot-foot upon the trail, without pause for discussion. And there was the scent of a four-footed creature here, too; but it was merged in, and subordinate to, the scent over which most wild creatures cry a halt: the scent of man.