Originally written in 1860 as number 12 in the "Calamus" series of the third edition of Leaves of Grass, this four-line poem was extensively revised by Whitman before he considered it finished in 1881. At one point, probably in 1867, he added a different opening line ("O Boy of the West!") and its present title, although he later dropped the opening line in order to make the poem a single interrogative sentence.
In the question it poses to his "eleve," or pupil, this love poem sums up Whitman's belief in the necessity of spiritual communion between men and boys. Using his familiar persona of an aged and wise benefactor, Whitman tells his "eleve" that if he neglects communion with Whitman—"if blood like mine circle not in your veins"—then there is no point in his trying to learn from his teacher. In other words, Whitman's message is that if the boy consciously or unconsciously excludes himself from the circle of men, then Whitman and his student have nothing in common and should sever their relationship. By stating the importance of love between males so strongly, Whitman reinforces a theme he develops in other poems such as "Song of the Open Road" and "Among the Multitude."
Bibliography
Allen, Gay Wilson. The Solitary Singer: A Critical Biography of Walt Whitman. 1955. Rev. ed. 1967. Chicago: U of Chicago P, 1985.
Miller, Edwin Haviland. Walt Whitman's Poetry: A Psychological Journey. Boston: Houghton Mifflin, 1968.
Whitman, Walt. Leaves of Grass: Comprehensive Reader's Edition. Ed. Harold W. Blodgett and Sculley Bradley. New York: New York UP, 1965.
____. Whitman's Manuscripts: "Leaves of Grass" (1860). Ed. Fredson Bowers. Chicago: U of Chicago P, 1955.