Quote 1
And each time the joyful bark that trembled in Buck's throat was twisted into a savage growl. (1.22)
Immediately after his capture, Buck’s domestic qualities give way to become more primitive.
Quote 2
With a roar that was almost lionlike in its ferocity, he again hurled himself at the man. (1.32)
The more Buck is provoked, the more he reverts to his primitive nature.
Quote 3
That club was a revelation. It was his introduction to the reign of primitive law, and he met the introduction halfway. The facts of life took on a fiercer aspect; and while he faced that aspect uncowed, he faced it with all the latent cunning of his nature aroused. (1.40)
Buck discovers latent qualities in himself that he previously did not know he had.
Quote 4
He had been suddenly jerked from the heart of civilization and flung into the heart of things primordial. (2.1)
Buck experiences a violent shift from the civilized world to the primitive one. He recognizes the extremity of such a change.
Quote 5
The snow walls pressed him on every side, and a great surge of fear swept through him--the fear of the wild thing for the trap. It was a token that he was harking back through his own life to the lives of his forebears; for he was a civilized dog, an unduly civilized dog, and of his own experience knew no trap and so could not of himself fear it. The muscles of his whole body contracted spasmodically and instinctively (2.12)
Buck retains memories of lives not his own.
Quote 6
And not only did he learn by experience, but instincts long dead became alive again. The domesticated generations fell from him. In vague ways he remembered back to the youth of the breed, to the time the wild dogs ranged in packs through the primeval forest and killed their meat as they ran it down. It was no task for him to learn to fight with cut and slash and the quick wolf snap. In this manner had fought forgotten ancestors. They quickened the old life within him, and the old tricks which they had stamped into the heredity of the breed were his tricks. They came to him without effort or discovery, as though they had been his always. And when, on the still cold nights, he pointed his nose at a star and howled long and wolflike, it was his ancestors, dead and dust, pointing nose at star and howling down through the centuries and through him. And his cadences were their cadences, the cadences which voiced their woe and what to them was the meaning of the stiffness, and the cold, and dark. (2.25)
Buck is not just an individual, but also a part of a long and communal history. He is the sum of all dogs that came before him and all that will come after.
Quote 7
The dominant primordial beast was strong in Buck, and under the fierce conditions of trail life it grew and grew. (3.1)
As Buck adapts to his new life, his primitive side becomes more prominent.
Quote 8
And strange Buck was to him, for of the many Southland dogs he had known, not one had shown up worthily in camp and on trail. They were all too soft, dying under the toil, the frost, and starvation. Buck was the exception. He alone endured and prospered, matching the husky in strength, savagery, and cunning. Then he was a masterful dog, and what made him dangerous was the fact that the club of the man in the red sweater had knocked all blind pluck and rashness out of his desire for mastery. He was preeminently cunning, and could bide his time with a patience that was nothing less than primitive. (3.22)
It is Buck’s primitive nature that allows him to survive in the frozen North where others of his kind have failed.
Quote 9
In the main they were the wild wolf husky breed. Every night, regularly, at nine, at twelve, at three, they lifted a nocturnal song, a weird and eerie chant, in which it was Buck's delight to join. (3.27)
Buck finds camaraderie with wild wolves because he recognizes his own primitivity in them.
Quote 10
It was an old song, old as the breed itself--one of the first songs of the younger world in a day when songs were sad. It was invested with the woe of unnumbered generations, this plaint by which Buck was so strangely stirred. When he moaned and sobbed, it was with the pain of living that was of old the pain of his wild fathers, and the fear and mystery of the cold and dark that was to them fear and mystery. And that he should be stirred by it marked the completeness with which he harked back through the ages of fire and roof to the raw beginnings of life in the howling ages. (3.28)
Buck finds camaraderie in the past generations of dogs like himself because they have all suffered similar hardships in the wild.
Quote 11
All that stirring of old instincts which at stated periods drives men out from the sounding cities to forest and plain to kill things by chemically propelled leaden pellets, the blood lust, the joy to kill--all this was Buck's, only it was infinitely more intimate. (3.33)
Buck finds a connection to his past when he experiences killing.
Quote 12
There is an ecstasy that marks the summit of life, and beyond which life cannot rise. And such is the paradox of living, this ecstasy comes when one is most alive, and it comes as a complete forgetfulness that one is alive. This ecstasy, this forgetfulness of living, comes to the artist, caught up and out of himself in a sheet of flame; it comes to the soldier, war-mad on a stricken field and refusing quarter; and it came to Buck, leading the pack, sounding the old wolf-cry, straining after the food that was alive and that fled swiftly before him through the moonlight. He was sounding the deeps of his nature, and of the parts of his nature that were deeper than he, going back into the womb of Time. He was mastered by the sheer surging of life, the tidal wave of being, the perfect joy of each separate muscle, joint, and sinew in that it was everything that was not death, that it was aglow and rampant, expressing itself in movement, flying exultantly under the stars and over the face of dead matter that did not move. (3.34)
Buck experiences joys and emotions in the frozen North that never would have been possible back in the Santa Clara Valley. Despite the hardships he suffers, there is an "ecstasy" involved in connecting with his primitivity.
Quote 13
As they circled about, snarling, ears laid back, keenly watchful for the advantage, the scene came to Buck with a sense of familiarity. He seemed to remember it all,--the white woods, and earth, and moonlight, and the thrill of battle...To Buck it was nothing new or strange, this scene of old time. It was as though it had always been, the wonted way of things. (3.37)
Although the adjustment to his new life was at first difficult, Buck begins to recognize that he belongs to the natural world more than he did to the ranch in California.
Quote 14
Buck stood and looked on, the successful champion, the dominant primordial beast who had made his kill and found it good. (3.42)
In killing, Buck established himself as a truly primitive creature.
Quote 15
Far more potent were the memories of his heredity that gave things he had never seen before a seeming familiarity; the instincts (which were but the memories of his ancestors become habits) which had lapsed in later days, and still later, in him, quickened and become alive again. (4.23)
Buck is revitalized by his instincts and his memories of the past. They help him adapt to the new surroundings.
Quote 16
Sometimes as he crouched there, blinking dreamily at the flames, it seemed that the flames were of another fire, and that as he crouched by this other fire he saw another and different man from the half-breed cook before him. This other man was shorter of leg and longer of arm, with muscles that were stringy and knotty rather than rounded and swelling. The hair of this man was long and matted, and his head slanted back under it from the eyes. He uttered strange sounds, and seemed very much afraid of the darkness, into which he peered continually, clutching in his hand, which hung midway between knee and foot, a stick with a heavy stone made fast to the end. He was all but naked, a ragged and fire-scorched skin hanging part way down his back, but on his body there was much hair. In some places, across the chest and shoulders and down the outside of the arms and thighs, it was matted into almost a thick fur. He did not stand erect, but with trunk inclined forward from the hips, on legs that bent at the knees. About his body there was a peculiar springiness, or resiliency, almost catlike, and a quick alertness as of one who lived in perpetual fear of things seen and unseen. (4.24)
Buck’s relationship with man takes many different forms. He feels a unique kinship to the man by the fire in his dreams that is different from anything he experiences in reality. Buck later reveals that this kinship has to do with fear.
Quote 17
At other times this hairy man squatted by the fire with head between his legs and slept. On such occasions his elbows were on his knees, his hands clasped above his head as though to shed rain by the hairy arms. And beyond that fire, in the circling darkness, Buck could see many gleaming coals, two by two, always two by two, which he knew to be the eyes of great beasts of prey. And he could hear the crashing of their bodies through the undergrowth, and the noises they made in the night. And dreaming there by the Yukon bank, with lazy eyes blinking at the fire, these sounds and sights of another world would make the hair to rise along his back and stand on end across his shoulders and up his neck, till he whimpered low and suppressedly, or growled softly, and the half-breed cook shouted at him, "Hey, you Buck, wake up!" Whereupon the other world would vanish and the real world come into his eyes, and he would get up and yawn and stretch as though he had been asleep. (4.25)
Buck gets more involved with this other dream-world as his transformation progresses and as he becomes more in tune with his primitive side.
Quote 18
Faithfulness and devotion, things born of fire and roof, were his; yet he retained his wildness and wiliness. He was a thing of the wild, come in from the wild to sit by John Thornton's fire, rather than a dog of the soft Southland stamped with the marks of generations of civilization. (6.8)
By the time he meets Thornton, Buck is already irrevocably changed from the dog he was when the story began.
Quote 19
His face and body were scored by the teeth of many dogs, and he fought as fiercely as ever and more shrewdly. Skeet and Nig were too good-natured for quarrelling--besides, they belonged to John Thornton; but the strange dog, no matter what the breed or valor, swiftly acknowledged Buck's supremacy or found himself struggling for life with a terrible antagonist. And Buck was merciless. He had learned well the law of club and fang, and he never forewent an advantage or drew back from a foe he had started on the way to Death. He had lessoned from Spitz, and from the chief fighting dogs of the police and mail, and knew there was no middle course. He must master or be mastered; while to show mercy was a weakness. Mercy did not exist in the primordial life. It was misunderstood for fear, and such misunderstandings made for death. Kill or be killed, eat or be eaten, was the law; and this mandate, down out of the depths of Time, he obeyed. (6.9)
Buck is unable to revert to his old tendencies, even when taken to a safe environment where the law of club and fang is no longer strictly necessary. His instincts have been awakened, and he cannot silence them.
Quote 20
He was older than the days he had seen and the breaths he had drawn. He linked the past with the present, and the eternity behind him throbbed through him in a mighty rhythm to which he swayed as the tides and seasons swayed. He sat by John Thornton's fire, a broad-breasted dog, white-fanged and long-furred; but behind him were the shades of all manner of dogs, half-wolves and wild wolves, urgent and prompting, tasting the savor of the meat he ate, thirsting for the water he drank, scenting the wind with him, listening with him and telling him the sounds made by the wild life in the forest, dictating his moods, directing his actions, lying down to sleep with him when he lay down, and dreaming with him and beyond him and becoming themselves the stuff of his dreams. (6.10)
Sitting by Thornton’s fire is directly contrasted with the fire in Buck’s dreams. Despite his love for Thornton, Buck feels an intense longing to be part of the other, primitive world.