Quote 37
There is a patience of the wild--dogged, tireless, persistent as life itself--that holds motionless for endless hours the spider in its web, the snake in its coils, the panther in its ambuscade; this patience belongs peculiarly to life when it hunts its living food; and it belonged to Buck as he clung to the flank of the herd, retarding its march, irritating the young bulls, worrying the cows with their half-grown calves, and driving the wounded bull mad with helpless rage. (7.29)
Buck assimilates aspects of the natural world into his own character.
Quote 38
And with the coming of the night, brooding and mourning by the pool, Buck became alive to a stirring of the new life in the forest other than that which the Yeehats had made, He stood up, listening and scenting. From far away drifted a faint, sharp yelp, followed by a chorus of similar sharp yelps. As the moments passed the yelps grew closer and louder. Again Buck knew them as things heard in that other world which persisted in his memory. He walked to the centre of the open space and listened. It was the call, the many-noted call, sounding more luringly and compellingly than ever before. And as never before, he was ready to obey. John Thornton was dead. The last tie was broken. Man and the claims of man no longer bound him. (7.42)
Buck becomes attuned to the natural world once he is a part of it.
Quote 39
And now the call came to Buck in unmistakable accents. He, too, sat down and howled. This over, he came out of his angle and the pack crowded around him, sniffing in half-friendly, half-savage manner. The leaders lifted the yelp of the pack and sprang away into the woods. The wolves swung in behind, yelping in chorus. And Buck ran with them, side by side with the wild brother, yelping as he ran. (7.46)
Buck’s transition from a passive listener of the call to a creature creating the call himself is the culmination of his character’s transformation.