And Arm and a Leg

As Moby Dick progresses, the reader notices less and less the intense and obsessive passion with which Captain Ahab hunts the white whale. However, in Chapters 100, and 106, this theme is brought to the forefront once again, when the Pequod meets the Samuel Enderby. Capitain Ahab hails the ship, asking them if they've come acrosst the white whale. Captain Boomer shows Ahab his ivory arm, which launches a long discussion about Moby Dick and his whereabouts.
This parallel between the two captains seems similar at first. Both having lost a limb to the whale, they excitedly begin talking about their respective stories, interrupting each other constantly. This is seen on page 337. "'It was he, it was he!' cried Ahab, suddenly letting out his suspended breath. 'And harpoons sticking in near his starboard fin.' 'Aye, aye - they were mine - my irons,' cried Ahab, exultingly - 'but on!'"
The difference is seen when Ahab requests a bearing. When asked if he tried to pursue the whale, Boomer replies, "Didn't want to try to: ain't one limb enough? What should I do without this other arm? And I'm thinking Moby Dick doesn't bite as much as he swallows." Ahab questions more and more until Bunger, a crew member of the Samuel Enderby, states, "This man's blood - bring the thermometer! - it's at the boiling point! - his pulse makes these planks beat!" This is the breaking point for Ahab, and he throws the man agains the deck of the ship, storming off back to the Pequod.
Once there, he splinters his ivory leg on the deck. This simple action symbolizes the difference between Ahab and Boomer. Both pursued Moby Dick, sacrificing something they could never get back, but Ahab couldn't let it go. The splintering of his leg shows his resolve and sanity slowly crumbling. But instead of leaving this obsession behind, on page 355, he blames Moby Dick even further. "Nor, at the time, had it failed to enter his monomaniac mind, that all the anguish of that then present suffering was but the direct issue of a former woe." These two simple excerpts foreshadow the direction that Ahab is heading, and solidify the fact that he can no longer turn back from his journey.