One's-self I sing, a simple separate person,
Yet utter the word Democratic, the word En-Masse.
Of physiology from top to toe I sing,
Not physiognomy alone nor brain alone is worthy for the Muse, I say
the Form complete is worthier far,
The Female equally with the Male I sing.
Of Life immense in passion, pulse, and power,
Cheerful, for freest action form'd under the laws divine,
The Modern Man I sing.
Whitman, writing here as a contemporary of Lincoln and Darwin, ushers in the modern age, and the modern  man : a man who is spiritual and was formed by and possibly obeys “laws divine,” sure, but at the same time, a man who submits himself over “freely” to “passion, pulse, power” and “cheer.” He lives his “immense” life to the fullest and doesn’t look back over his shoulder to a past that is becoming rapidly antiquated. 

Ones-Self I Sing