Sourdough had aged a good deal during the past year, but despite the twist in his near fore leg, which caused him to limp slightly, the old dog still held his own as despotic ruler of all the dogs in that locality. But for a good many years he had done no work of any kind, neither had he had any very serious fighting or come in contact with northland dogs. His swiftest movements would have seemed clumsy and slow to the working husky, inured to the comparative wildness of trace life in the north. But his morose arrogance and ferocity had suffered no diminution, as was shown by the fact that he flew straight for Jan's throat directly he set eyes on the big hound. "Call your dog off, Sergeant, or he'll be killed," shouted Dick. Sergeant Moore spake no word. In his queer heart intelligence of Dick's fame rankled bitterly, yet not so bitterly as the fact of Jan's return to barracks. His obsession made him certain in his own mind that the redoubtable Sourdough could certainly kill any dog. And so he spake no word while Sourdough flew at Jan. And for Jan, as he caught sight in the gloaming of his ancient enemy, his hackles had risen very stiffly, his pendent lips had twitched ominously. Jan was perfectly well aware that the killing of Sourdough or any other dog he had seen since his return to cities would be a supremely easy matter for him. Indeed it would be for almost any dog having his experience of the wild. And having in his simple dog mind no shadow of a reason for sparing Sourdough, of all creatures that walked, one may take it that Jan savored with some joyousness the prospect of the killing which Sourdough's snarling rush presented to him. He received that rush with a peculiar screwing thrust of his left shoulder, the commonest trick among fighting-dogs in the northland, but one for which old Sourdough seemed totally unprepared, since he made no apparent preparation to withstand it, and as an inevitable consequence was rolled clean over on his back by the force of his own impetus, scientifically met. That, by all the rules in the northland game of which Jan was a past-master, brought Sourdough within seconds of his end. The throat was exposed; the deadly underhold, given which no dog breathing could evade Jan. And at that moment came Dick's voice in very urgent and meaning exhortation: "Back, Jan! Don't kill him. He's too old. Back--here--Jan!" Jan's jaws had parted for the killing grip. His whole frame was perfectly poised for the thrust from which no dog placed as Sourdough was could possibly escape. A swift shudder passed through him as though his sovereign's words reached him on a cold blast, and, stiff-legged, wondering, his shoulder hair all erect, and jaws still parted for the fray, Jan stepped back to Dick's side. "You'll have to keep that old tough in to heel if you mean to save him, Sergeant," said Captain Arnutt. "You can't expect Jan to lie down to him. Why don't you keep him in to heel, man?"