Whitman takes special care to describe both the female and the male form in “I Sing the Body Electric”. In section 5, he approaches the female body, describing it as a “nimbus form” that is “lost in the cleave of the clasping and sweet-flesh’d day”.
I find myself also drawn to the comparison of the female form to the moon because of Whitman’s non-binary description of the body and soul throughout his writing. He constantly makes distinctions between the two as separate parts, but insists that they exist as one entity. The way I understand this is that without separate, binary parts we have nothing– dark does not exist without light, the moon without the sun, etc. I believe that in these sections in which Whitman is describing the male and female forms, he is merely describing two separate parts of one whole: the man and woman united. The moon cannot function without the sun, nor the sun without the moon. The moon must rely on the light of the sun to illuminate the night, while the sun must rely on the moon to provide light while it attends to another part of the world.
The “nimbus form” of the moon is a symbol that is recognized with feminine power. The moon’s power is frequently associated with the occult, supernatural, and the clandestine. The moon seems to have an eerie, hidden quality about it because it never shows it’s true form– it is always illuminated and reflective of the sun. Although this seems to have a negative connotation to it, Whitman recognized the power of this feminine form as something to be reckoned with in its own right by endowing it with these supernatural powers. Whitman suggests that the form of the woman has a “fierce undeniable attraction” and describes being drawn by it’s “breath”; this attraction seems uncontrollable and natural as Whitman himself is drawn in by mere breath. I found it easy to associate this part of the poem to the moon by comparing this to the tide: just as breath goes in and out and Whitman has an undeniable draw to it, the moon controls the tide constantly bringing it in and out by mere unseen force.
Suggesting that the form gets lost in the day time points to the celestial body being the moon also as the moon is not visible during the day. The feminine form becomes “lost in the cleave of the clasping and sweet flesh’d day”. Whitman gives a more concrete and solid description to the day time, describing it as “flesh’d”; again, a binary/ non-binary comparison against the “supernatural” female. Occult and supernatural power can’t exist without traditional and concrete power, and vice-versa.
Perhaps Whitman means to suggests that our bodies are merely the pieces of the puzzle to unite the soul; to unify and transcend, just as the moon and sun unify to create both a night and day sky for us.
Interesting meditation on this lunar imagery. In a way, by gravitating towards lunar imagery, Whitman partakes in a long-standing figure, as you note, for femininity. The moon, as you note, is “always illuminated by and reflective of the sun,” which seems to suggest a certain priority–a priority we see as well when Whitman describes men as truly passionate, and women as those who give birth to men. The secondary quality is sort of embedded in the metaphor, even as you note the broader, radical unity he is implying here.