London uses a rather austere style in "To Build a Fire," which is typical of Naturalist writing, and this makes his rare usage of figurative language particularly poignant. This simile, for example, helps highlight the story's overarching argument about instinctual and scientific knowledge:
The blood was alive, like the dog, and like the dog it wanted to hide away and cover itself up from the fearful cold.
By comparing the man's blood to the dog, London highlights that the man possesses a deep-seated instinctual aversion to the cold temperature. In the same way that the dog wants to huddle up and somehow hide itself from the dangerous temperatures, the man's blood—that is, an essential part of his ability to go on living—instinctually wants to "cover itself up." Unlike the dog, however, the man has ignored this instinct in favor of reason, a choice that ultimately leads to his death.
This simile also illustrates the indifference of nature and how the man's fate is shaped by forces beyond his control. In this moment, the man needs his hands to build a fire, but his body, which is behaving in a completely natural manner, betrays him by reducing blood flow to his extremities.
In this simile, which occurs at the climax of the story, London compares nature to civilization and addresses a major flaw in his protagonist's thinking:
High up in the tree one bough capsized its load of snow. This fell on the boughs beneath, capsizing them. This process continued, spreading out and involving the whole tree. It grew like an avalanche, and it descended without warning upon the man and the fire, and the fire was blotted out! Where it had burned was a mantle of fresh and disordered snow.
The man was shocked. It was as though he had just heard his own sentence of death.
In this passage, London compares the sound of snow falling on the fire to a death sentence being issued. In doing so, he shows how the man can only understand this catastrophic event within the context of human society and law. When he hears the noise of the snow blotting out the fire, he perhaps interprets it as the the sound of a striking gavel or the voice of a jury foreman reading out a verdict. In other words, he views the event as a deliberate act of judgment.
In reality, however, nature is not passing any type of judgment on the man as a judge or jury would, and the event has occurred due to a combination of random chance and the man's own carelessness. Although this simile explicitly compares nature to human society, then, London implicitly underscores their differences.
