In a word, the poem has no rhyme scheme. That is, the end-words do not echo any other end-words. Technically, it would be called “blank verse” although that term implies some attention to poetic “feet.” This is not to say that the poet was insensitive to the details of his words’ and lines’ sounds, lengths, rhythms, etc. In fact it is a “poem” mainly in the sense that it is broken into lines (of uneven length) and stanzas (of seemingly arbitrary length). But the absence of formal structure is integral to the poem’s sense, to its primary metaphor: the emotions come first (“feeling is first”) before the oral or written expression of those feelings (thus, the linguistic terms, such as “syntax,” “paragraph,” “parenthesis”). He is differentiating between man-made expression (“the best gesture of my brain” i.e. his ability to give form and expression to his feelings) and natural emotion/ expression (“your eyelids’ flutter), celebrating the primary feelings rather that the imperfect attempts by Mankind to give them order (that is poetic "rules" such as rhyme).