Old longings nomadic leap, Chafing at custom’s chain; Again from its brumal sleep Wakens the ferine strain.The Call of The Wild 
The novel opens with the first quatrain of John Myers O'Hara's poem, Atavism, published in 1902 in The Bookman. The stanza outlines one of the main motifs of the novel: that Buck, raised in the "sun-kissed" Santa Clara Valley, will revert to innate instincts and characteristics of his wolf heritage.
The themes are conveyed through London's use of symbolism and imagery which, according to Labor, vary in the different phases. The imagery and symbolism in the first phase, to do with the journey and self-discovery, shows physical violence, with strong images of pain and blood. In the second phase fatigue becomes a dominant image and death is a dominant symbol as Buck comes close to being killed; the third phase shows a period of renewal and rebirth and takes place in the spring; the fourth phase of reverting to nature is placed in a vast and "weird atmosphere", a place of pure emptiness.
The setting is allegorical: the south represents the soft, materialistic world; the north symbolizes a world beyond civilization and is inherently competitive. The harshness, brutality, and emptiness in Alaska reduce life to its essence, as London learned, and is shown in Buck's story. Buck defeats Spitz, the dog who symbolically tries to get ahead and take control. When Buck is sold to Charles, Hal, and Mercedes, he finds himself in a camp that is dirty. They treat their dogs badly; they are artificial interlopers in the pristine landscape. Conversely, Buck's next masters, John Thornton and his two companions, are described as "living close to the earth". They keep a clean camp, treat their animals well, and represent man's nobility in nature. Unlike Buck, Thornton loses his fight with his fellow species, and not until Thornton's death does Buck revert fully to the wild and his primordial state.
The characters too are symbolic of types. Charles, Hal and Mercedes symbolize vanity and ignorance, while Thornton and his companions represent loyalty, purity, and love. Much of the imagery is stark and simple with an emphasis on images of cold, snow, ice, darkness, meat, and blood.
London varied his prose style to reflect the action. He wrote in an over-affected style in his descriptions of Charles, Hal, and Mercedes' camp as a reflection of their intrusion in the wilderness. Conversely when describing Buck and his actions, London wrote in a style that was pared down and simple—a style that would influence and be the forebear of Hemingway's style.
The story was written as a frontier adventure and in such a way that it worked well as a serial. As Doctorow points out, it is good episodic writing that embodies the style of magazine adventure writing popular in that period. "It leaves us with satisfaction at its outcome, a story well and truly told," he said.