Life streamed through him in splendid flood, glad and rampant, until it seemed that it would burst him asunder in sheer ecstasy and pour forth generously over the world.
"Never was there such a dog," said John Thornton one day, as the partners watched Buck marching out of camp.
"When he was made, the mould was broke," said Pete.
"Py jingo! I t'ink so mineself," Hans affirmed.
They saw him marching out of camp, but they did not see the instant and terrible transformation which took place as soon as he was within the secrecy of the forest.

He no longer marched.

At once he became a thing of the wild, stealing along softly, cat-footed, a passing shadow that appeared and disappeared among the shadows.

He knew how to take advantage of every cover, to crawl on his belly like a snake, and like a snake to leap and strike.

He could take a ptarmigan from its nest, kill a rabbit as it slept, and snap in mid air the little chipmunks fleeing a second too late for the trees.