I, now thirty-seven years old in perfect health begin,
Whitman was 37 years old in 1856. But this line (in fact, this whole stanza and the stanza following) was not part of either the original 1855 poem or the revised 1856 version. Whitman was a constant reviser of his own work, and there are many differences among different editions of “Song of Myself” (which didn’t even originally have a title).
The boast about his age and health was added in a later edition, by which time the poet was well past his thirties.
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