Oh captain my captain lines 5-8 can best be summarized as

But O heart! heart! heart!
   O the bleeding drops of red,
      Where on the deck my Captain lies,
         Fallen cold and dead.

The sailor calls out again, but this time it isn’t for the captain.He belts out the word “heart,” and this could mean that he is shouting out a) to his captain to keep heart, as in not to give up, or b) to his own heart, as if in pain. We think you can read this either way. If you read it the first way, with the heart representing the captain’s will, then you’re dealing with a symbol, as some part of the captain is used to represent an abstract quality (his will or courage).If you read it the second way, though, and think the speaker is calling out to his own heart, then you’ve got an apostrophe on your hands, friend-o. This is a call to an abstract thing that can’t possibly answer back. It’s a cliché to speak from the heart, but, really, hearts have no mouths, so they don’t speak very well.When you think heart, though, you do think blood. It turns out that there is a lot of it here.All of a sudden, drops of blood are on the deck of the ship, and the speaker notices that his captain is dead. 

That’s nice! sounds really fun.