All the pulses of the world, Falling in they beat for us, with the Western movement beat, Holding single or together, steady moving to the front, all for us, Pioneers! O pioneers!
Again we have the image of a unified group, with all the world seeming to pulse a rhythmic beat, holding the group together.
That beat makes us think of a heart. It makes this group sound like one great organism, whose heartbeat spans the world. Whoa. No need to get all New-Agey on us, Walt.
There's also the sense that our speaker feels that the whole word (all its pulses, at least) are going into this movement. As if these are the chosen people. It's "all for us," he says.
We're also starting to think that his definition of pioneers might include more people than simply the guys with axes and fur hats tramping around beyond the borders of civilization.
But who else could the pioneers be?
Life's involv'd and varied pageants, All the forms and shows, all the workmen at their work, All the seamen and the landsmen, all the masters with their slaves, Pioneers! O pioneers!
Our speaker is headed to a show! Okay, not really. But here he talks about life as a kind of parade—shows, forms, pageants. It's all very exciting.
And what are those, exactly? Life's pageants, forms, and shows? Well, we don't have any specific image for these. Our guess is that he means just about everything. Springtime could be a show; buildings and trees are forms; this whole civilization thing could be one crazy pageant. As far as we know, he's including everything here. Whitman was a very inclusive guy.
He doesn't say it quite as explicitly in this stanza as he did in the last, but our sense is that these forms and shows, like the pulses of the world, are "for us."
There's that sense of that unity again, of all the world united in this march of ours, we pioneers of the human race.
Here, it seems that just about everyone's a pioneer—masters, slaves, sailors, and landlubbers alike.