Within the genre of fantasy and mythology, Tolkien is able to establish gradations of good and evil and it is worth noting how quickly enemies became allies. Bilbo's wound at the end of the chapter is a cliffhanger that repeats the same scene that ended Chapter 4. As far as the themes of consciousness and knowledge are concerned, Bilbo needs to avoid rocks and stones, as they tend to knock him out. Still, if we follow the trajectory of Christian allusions attached to Bilbo, his recovery in the next chapter can be considered as a resurrection, much as his return "home" can parallel a final departure/ascension. Most important, Bilbo proves himself as the savior-hero of the scene, not by fighting, but by his knowledge and insight. His "eyes were seldom wrong" and he is the one who sees "the sudden gleam in the gloom"...a sight that made his heart leap." His announcement of the Eagles' approach is what enables the victory. As a final irony, a scene of birds flying overhead or a cry of "The Eagles" or "The Birds" is usually a symbol of doom. Here, Bilbo's cry of "The Eagles" is a herald of something positive‹though it may account for his own unfortunately injury. Chapter Eighteen: The Return Journey

When Bilbo regains consciousness, he finds that he is alone and he has to take his ring off so that the individuals who were sent for him can find him. After recovering in the company of Gandalf, Bilbo makes his way back home and their journey‹though covering the same perilous terrain‹is far more pleasant and mild than it was the first time. As Bilbo says, "So comes snow after fire, and even dragons have their ending."
Analysis:

In terms of narrative structure, this chapter and the next one offer two endings to the story. This chapter gives us a visual panorama of the landscape of Middle Earth and it establishes Bilbo and Gandalf as characters who will reappear in later works. Chapter 17 presented a battle involving five armies and while this has no direct reference to any anterior work, it does seem to be a threat to the peace of the world. The images of Chapter 18 are all muted, pale and subdued. "A new peace came over the edge of the Wild." We can argue about whether or not this is a case of what Ruskin calls the "pathetic fallacy"‹and indeed, we ought to always bear this in mind when reading fantasy work. It is one thing when the terrain or setting is passive and the emotions of the actors are projected upon the scene.