I found mention of this paper over at Tingle Alley. An excerpt of the paper:
My survey of around thirty prominent twentieth-century Southern authors has led me to conclude, without fear of refutation, that there is indeed a single, simple, litmus-like test for the quality of Southernness in literature, One easily formulated into a question to be asked of any literary text and whose answer may be taken as definitive, delimiting, and final. The test is: Is there a dead mule in it? As we shall see, the presence of one or more specimens of Equus caballus x asinus (defunctus) constitutes the truly catalytic element, the straw that stirs the strong and heady julep of literary tradition in the American South.
I find this immensely funny, but as a Southerner, a writer, and a fan of 20th Century Southern literature, I also find it a bit disconcerting and perhaps even slightly offensive.
Yet, I am also overly drawn to the idea of attempting to work a dead mule into the fiction I am currently writing…