The story went that in his youth Sourdough had led a team of sled-dogs, and that he had saved Moore’s life on one occasion when every one of his team-mates had either died or deserted his post.  He was of the mixed northern breed whose members are called huskies, but he was bigger and heavier than most huskies and weighed just upon a hundred pounds.  A wagon-wheel had once gone over his tail (when nine dogs out of ten would have lost their lives by receiving the wheel on their hind quarters), and this appendage now had a curious bend in the middle of it, making it rather like a bulldog’s “crank” tail, but long and bushy.  He was far from being a handsome dog; but he looked every inch a fighter, and there was a certain invincibility about his appearance which, combined with his swiftness in action and the devastating severity of all his attacks, served to win for him the submissive respect of almost every dog he met.  Occasionally, and upon a first meeting, some careless, undiscerning dog would overlook these qualities.  The same dog never made the same mistake a second time.

Dick Vaughan made it his business to be on hand when Sourdough first met Jan.  When ordered to do so, Jan had learned to keep his muzzle within a yard of Dick’s heels, and that was his position when Sergeant Moore came striding across the yard with Sourdough.  Jan’s hackles rose the moment he set eyes on the big husky.  Sourdough, as his way was, glared in another direction.  But his hackles rose also, and his upper lip lifted slightly as the skin of his nose wrinkled.  Clearly there was to be no sympathy between these two.

Suddenly, and without apparently having looked in Jan’s direction, Sourdough leaped sideways at him, with an angry snarl.

“Keep in—­Jan; keep in—­boy!” said Dick, firmly, as he jumped between the two dogs.

“Who gave you permission to bring that dog here?” snapped the sergeant at Dick.

“Taking care of him for Captain Arnutt, sir,” was the reply.

“H’m!  Well, see you take care of him, then, and keep him out of the way.  Sourdough’s boss here, and if this one is to stay around, the sooner he learns it the better.”

“Yes, sir.  He’s thoroughly good-tempered and obedient, though he is such a big fellow,” said Dick, still manoeuvering his legs as a barrier betwixt the two dogs.

“It’s little odds how big he is,” growled the sergeant.  “He’ll have to learn his lesson, an’ I guess Sourdough will teach him.”

Just then Sourdough succeeded in evading Dick and got well home on Jan’s right shoulder with a punishing slash of his razor fangs.  Jan gave a snarl that was half a roar.  His antipathy had been aroused at the outset.  Now his blood was drawn.  He had been ordered to keep to heel, but—­

“Keep in, there—­Jan; keep in—­keep in!”

The warning came not a second too soon.  Almost the hound had sprung.

“Would you call your dog off, sir?” said Dick.