The speaker turns the act of screaming into something to be studied. With a knife already under the skin, they set out to explore the "history of the scream," following it through the body: the tongue, the back of the mouth, the lungs. The knife works as both a literal threat and a tool of inquiry, so the poem feels like a dissection of sound itself.
The mood is tense and strangely cold. The speaker sounds calm and observant, yet the images are harsh. The lungs have "no saliva to give, / no tears to distribute," which suggests a body drained and dry, past the point of crying. The stretched-out spelling of "sscccrrrreeeeaaaaam" makes us hear the sound lengthen, like a plane leaving a runway. In the final lines, the throat is a black cave that shifts into "an unknown color" as the scream escapes. That answers the title's question with a mystery: the scream can be felt and heard, but it resists being named or pinned down.