What is the purpose of the decapitated hen metaphor in the opening paragraph of the essay?

The metaphor of the decapitated hen, while gruesome, is what allows Woolf to set up the structure of her essay for the reader. She wants readers to know that her task of discussing the "craft" or writing is actually not possible, and as such her talk will explain why that is so. By invoking the image of the decapitated hen, Woolf stirs up many ideas that will continue to percolate throughout the essay, namely the idea that words are "wild," circular in nature (having multiple meanings), and that they refuse any attempt to constrain them. Like her description of words, Woolf's essay itself becomes an exercise in circularity as she shows how the mind builds ideas on top of each other and dictates interpretation.

What role does literary allusion play in the essay?