“These are the most interesting and mysterious years in Whitman’s biography, and now we have this major journalistic series right in the middle of it,” said Ed Folsom, the editor of The Walt Whitman Quarterly Review, the online journal that is publishing the series in its spring issue.

“One of Whitman’s core beliefs was that the body was the basis of democracy,” Mr. Folsom, a professor of English at the University of Iowa, continued. “The series is a hymn to the male body, as well as a guide to taking care of what he saw as the most vital unit of democratic living.”

The series was discovered last summer by Zachary Turpin, a graduate student in English at the University of Houston who was browsing in digitized databases of 19th-century newspapers, entering various pseudonyms that Whitman, a prolific journalist, was known to have used.

“It’s kind of a sickness I have in off-hours,” Mr. Turpin said in an interview.

During one search, up popped a brief reference in The New-York Daily Tribune on Sept. 11, 1858, to a series on manly health by “Mose Velsor,” one of Whitman’s favorite pen names, which was about to appear in another paper, The New York Atlas. (While his notebooks have long been known to contain a handwritten draft of an advertisement for a series on “manly health,” scholars have never known whether Whitman — much of whose voluminous journalism has been lost — had ever actually written such a series.)

Image An advertisement for Whitman’s series “Manly Health and Training” in The New York Atlas. Credit... American Antiquarian Society

When Mr. Turpin ordered microfilm of the relevant issues of The Atlas, which survive in only a few libraries and have not been digitized, he was stunned to find 13 installments.

“It took about 24 hours for it to sink in,” he said.

“Manly Health and Training” was published in weekly installments starting in September 1858, a time when Whitman, then 39, was licking his wounds over the flop of the first two editions of “Leaves of Grass” and churning out hundreds of words a day as a journalist.