As Lad went down the mongrel deftly shifted his unprofitable shoulder grip to a far more promisingly murderous hold on his fallen victim's throat. A cat has five sets of deadly weapons--its four feet and its jaws. So has every animal on earth--human and otherwise--except a dog. A dog is terrible by reason of its teeth. Encase the mouth in a muzzle and a dog is as helpless for offensive warfare as is a newborn baby. And Lad was thus pitiably impotent to return his foe's attack. Exhausted, flung prone to earth, his mighty jaws muzzled, he seemed as good as dead. But a collie down is not a collie beaten. The wolf-strain provides against that. Even as he fell Lad instinctively gathered his legs under him as he had done when he tumbled from the car. And, almost at once, he was on his feet again, snarling horribly and lunging to break the mongrel's throat-grip. His weariness was forgotten and his wondrous reserve strength leaped into play. Which was all the good it did him; for he knew as well as the mongrel that he was powerless to use his teeth. The throat of a collie--except in one small vulnerable spot--is armored by a veritable mattress of hair. Into this hair the mongrel had driven his teeth. The hair filled his mouth, but his grinding jaws encountered little else to close on. A lurching jerk of Lad's strong frame tore loose the savagely inefficient hold. The mongrel sprang at him for a fresh grip. Lad reared to meet him, opposing his mighty chest to the charge and snapping powerlessly with his close-locked mouth. The force of Lad's rearing leap sent the mongrel spinning back by sheer weight, but at once he drove in again to the assault. This time he did not give his muzzled antagonist a chance to rear, but sprang at Lad's flank. Lad wheeled to meet the rush and, opposing his shoulder to it, broke its force. Seeing himself so helpless, this was of course the time for Lad to take to his heels and try to outrun the enemy he could not outfight. To stand his ground was to be torn, eventually, to death. Being anything but a fool Lad knew that; yet he ignored the chance of safety and continued to fight the worse-than-hopeless battle. Twice and thrice his wit and his uncanny swiftness enabled him to block the big mongrel's rushes. The fourth time, as he sought to rear, his hind foot slipped on a skim of puddle-ice. Down went Lad in a heap, and the mongrel struck. Before the collie could regain his feet the mongrel's teeth had found a hold on the side of Lad's throat. Pinning down the muzzled dog, the mongrel proceeded to improve his hold by grinding his way toward the jugular. Now his teeth encountered something more solid than mere hair. They met upon a thin leather strap. Fiercely the mongrel gnawed at this solid obstacle, his rage-hot brain possibly mistaking it for flesh. Lad writhed to free himself and to regain his feet, but seventy-five pounds of fighting weight were holding his neck to the ground.