Whitman expands on his curiosity about Being or existence.
Even if there weren't beings more sophisticated than the shell of a "quahaug" (a kind of clam) it would still be amazing.
But he's more than just a shell; he's full of living energy.
This energy makes it intensely pleasurable to touch things and people. Touch is the most important physical sense for Whitman. He can't stand to do anything more than touch someone. Otherwise he'd explode! Maybe not, but something cool would probably happen.