From The Call of the Wild, by Jack London:
“They were new dogs, utterly transformed by the harness. All passiveness and unconcern had dropped from them. They were alert and active, anxious that the work should go well, and fiercely irritable with whatever, by delay or confusion, retarded that work. The toil of the traces seemed the supreme expression of their being, and all that they lived for and the only thing in which they took delight.”
Read The Call of the Wild, by Jack London, free online at Project Gutenberg. Published in 1903, the story is set in the Yukon during the 1890’s Klondike Gold Rush—a period when strong sled dogs were in high demand. The novel’s central character is a dog named Buck, who is living on a ranch in California as the story opens. Stolen from his home and sold into the brutal existence of an Alaskan sled dog, Buck is forced to adjust and survive, relying on his own instincts and the lessons he learns.
Jack London lived for most of a year in the Yukon collecting material for the book. The story was serialized in the Saturday Evening Post in the summer of 1903, and a month later it was released in book form. The novel’s great popularity and success made a reputation for London. Much of its appeal derives from the simplicity with which London presents the themes in an almost mythical form. As early as 1908 the story was adapted to film and it has since seen several more cinematic adaptations. (Edited from the Wikipedia entry.)