The 1860 version of the poem is divided into 26 sections with 147 lines. The version from 1881 has only nine sections, but most of the lines are the same. The entire poem is written in free verse, a poetic form Whitman helped pioneer.
Free verse has no regular meter or rhyme scheme. Sounds like total chaos, right? But Whitman's style of free verse is one of the most easily recognizable forms in English-language poetry. It consists of lines of varying length, some so long that they have to be carried over and indented in what looks like small paragraphs. So, remember that when you see what looks like an indented line, it's actually part of the line above it. Why is this important? Because each line is meant to be read in a single breath. Otherwise, you might think to throw an unnecessary pause in the middle of a word or sentence.
There are a couple of other ways to recognize Whitman's free verse. First, he repeats himself like crazy. For example, he frequently uses a rhetorical device called "anaphora." That's when you repeat the same word at the start of several lines in a row. Lines 13-16 all begin with the word "Others," and lines 34-37 begin with the word "Looked." He also repeats the same words and phrases several times throughout the poem, like a musician returning to a theme. He layers these repetitions so subtly into the poem that they are easy to miss. For instance, did you catch that the beginning of the last line, "Great or small," is the same phrase that he used earlier when he compared people to actors performing roles of various sizes?
Another essential Whitman device is the catalogue, or list. In Section 16, he provides a catalogue of evil acts that he has committed. Whitman's poetry is like a big umbrella trying to bring as many things as possible beneath its cover.
Taken together, these and other techniques produce a familiar chant-like quality that characterizes all of Whitman's work. Although his poems lack a traditional meter, they contain incredibly complex and varied rhythms. Notice how he mixes the word "wanting" into the list of sins he has committed, in a way that produces stops and starts and pauses:
The wolf, the snake, the hog, not wanting in me,
The cheating look, the frivolous word, the adulterous wish, not wanting,
Refusals, hates, postponements, meanness, laziness, none of these wanting.